This article presents a modulation-free laser stabilization technique that resolves the inherent trade-off between frequency noise suppression and locking range by integrating a cavity-coupled Mach-Zehnder interferometer with an aided acquisition system (CCMZI-AAQ). Implemented on a compact 5.43 mm² silicon nitride (SiN) photonic integrated chip, the system uses an electronic aided acquisition (AAQ) mechanism to guide the laser’s frequency back toward the narrow resonance of an on-chip micro-ring resonator when it drifts too far. Once within the narrow locking range, a high-gain feedback loop takes over to tightly stabilize the laser. The authors experimentally demonstrate that this method extends the locking range by over an order of magnitude to 3.95 GHz, the full free spectral range of the resonator, while achieving more than 36 dB of frequency noise suppression at a 1 kHz offset, all without degrading the noise performance. This scalable approach enables the development of integrated, low-noise lasers with exceptional long-term stability for applications like fiber sensing and optical communication.

Mohamad Hossein Idjadi et al. (2024), Optics Express

This paper presents a groundbreaking watt-class silicon photonics amplifier based on large mode area (LMA) waveguide technology, achieving over 1 W on-chip output power within a compact ~4.4 mm² footprint. Using a thulium-doped aluminum oxide gain layer, the device addresses the limitations of integrated photonics by offering high energy storage and minimal parasitic lasing. With a net gain of 16.5 dB and conversion efficiencies up to 66%, it surpasses many fiber-based amplifiers while enabling applications in compact satellites, medical lasers, and high-precision sensing. This innovation paves the way for high-power, integrated photonics, replacing bulky benchtop systems and expanding the capabilities of laser-based technologies.

Singh et al. (2024), Nature Photonics

Here, we investigate the factors that could influence the phase noise of microwave signals generated with dual-pumped soliton microcombs, including the polarization, amplitude noise, and phase noise of the two pumps. We demonstrate a 25.25 (12.63) GHz microwave with phase noise reaching −112(−118) dBc/Hz at a 10 kHz offset frequency, surpassing the performance of previous reports on microwave generation using free-running Si3N4 soliton microcombs, even those generated with higher Q microresonators.

Liu et al. (2024), Optics Letters

Here we demonstrate a high-energy silicon photonics-based passively Q-switched laser with a compact footprint using a rare-earth gain-based large-mode-area waveguide. We demonstrate high on-chip output pulse energies of >150 nJ and 250 ns pulse duration in a single transverse fundamental mode in the retina-safe spectral region (1.9 µm), with a slope efficiency of ~40% in a footprint of ~9 mm2. The high-energy pulse generation demonstrated in this work is comparable to or in many cases exceeds that of Q-switched fibre lasers. This bodes well for field applications in medicine and space.

Singh et al. (2024), Nature photonics

We introduce a high-performance external cavity diode laser constructed with AlGaAs-Si 3 N 4 hybrid integration, exhibiting a narrow linewidth of 18 kHz, a tuning range of 62.9 nm, and side mode suppression ratio better than 45 dB. The Si3N4 chip in this paper is taped out at LIGENTEC.

Chen et al. (2023), IEEE

Here we present a voltage-tunable, on-chip integrated optical parametric oscillator based on an alternating-dispersion dimer fabricated by LIGENTEC SA, allowing us to tune the emission over nearly 20 THz near 1550 nm. Integration of this scheme on a chip opens up the possibility of compact and low-cost voltage-tunable parametric oscillators with diverse application possibilities.

Pidgayko et al. (2023), Optica

Based on the chips fabricated at Ligentec, we report >50-fold amplification of 1 GHz-repetition-rate chirped femtosecond pulses in a CMOS-compatible photonic chip to 800 W peak power with 116 fs pulse duration.

Gaafar et al. (2023), arXiv

On-chip amplification of ultrafast pulses remains challenging due to the inherently small mode area and high-optical nonlinearity in integrated waveguides. Here we demonstrate our work of ultrafast pulse amplification on the silicon nitride chips fabricated by LIGENTEC.

Gaafar et al. (2023), IEEE

We demonstrate a heterogeneously integrated III-V-on-silicon-nitride mode-locked laser with 710 MHz repetition rate. A versatile two-step micro-transfer printing approach is employed to enable low-loss integration on a commercial foundry low-index photonic platform.

Poelman et al. (2023), CLEO 2023 conference contribution

Here, we design and experimentally demonstrate a proof-of-principle integrated silicon nitride device capable of imprinting the Talbot phase relation onto in-phase optical combs and generating the two-fold self-images at the output. We show that the GHz-repetition-rate bright and dark pulse trains can be doubled without affecting their spectra as a key feature of the temporal Talbot effect. The designed chip can be electrically tuned to switch between pass-through and repetition-rate-multiplication outputs and is compatible with other related frequencies.

Wu et al. (2023), Communications Physics

A discrete, tunable photonic integrated laser is showcased for multiwavelength spectroscopy of CO2, H2S, and H2O. The laser combines an AlGaInAsSb/GaSb type-I quantum well-reflective semiconductor optical amplifier with a Si3N4 photonic integrated circuit (PIC). Operating at room temperature, the laser emits at 2670.42, 2629.12, and 2594.27 nm, with mW-level average powers.

Ojanen et al. (2023), Laser & Photonics Review

We have designed and fabricated a hybrid integrated laser source with full C-band wavelength tunability and high-power output. The external cavity laser is composed of a gain chip and a dual micro-ring narrowband filter integrated on the silicon nitride photonic chip to achieve a wavelength tuning range of 55 nm and a SMSR higher than 50 dB. Through the integration of the semiconductor optical amplifier in the miniaturized package, the laser exhibits an output power of 220 mW and linewidth narrower than 8 kHz over the full C-band.

Chen et al. (2023), Optics Express

We demonstrate CMOS-compatible, integrated, high energy Q-switched lasers in the eye-safe window (1.9 µm), with an on-chip output pulse energy of 80 nanojoules at a repetition rate of <1 MHz with single fundamental mode operation in a compact footprint.

Singh et al. (2023), CLEO 2023 conference contribution

In this work, we demonstrate large mode area (LMA) waveguide based CMOS compatible watt-class power amplifier with an on-chip output power reaching ~ 1W within a footprint of ~4mm2. The power achieved is comparable and even surpasses many fiberbased amplifiers. The thickness of the thulium doped aluminum oxide gain medium (Tm3+:Al2O3) is 1.35 µm on top of a silica cladding layer within which a 800 nm thick SiN layer is buried (such a thick SiN allows seamless integration to conventional nonlinear photonics components).

Singh et al. (2023)

We propose a hybrid integrated self-injection locked (SIL) narrow linewidth laser with adjustable feedback intensity, through an adjustable Sagnac loop reflector (ASLR) coupled to a high- Q micro-ring resonator. The intrinsic linewidth is reduced to 60 Hz, and the locking range without phase compensation is extended to 6.3 GHz. This work has important application value in the field of coherent detection and precision metrology.

Su et al. (2023), IEEE Xplore

We designed and fabricated two on-chip tunable lasers for CV-QKD (continuous-variable-quantum key distribution), and demonstrated a high-performance system based on these sources. Because of the high output power, fine tunability, and narrow linewidth, the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals, center wavelength alignment of nonhomologous lasers, and suppression of untrusted excess noise.

Li et al. (2023), Photonics Research

We demonstrate a high-performance integrated laser exhibiting broad wavelength tuneability near a 2.6 µm wavelength region. The laser is based on a Si3N4 photonic integrated circuit incorporating a tunable reflector and a AlGaInAsSb/GaSb quantum-well gain element. A tuning range of 170 nm (2474–2644 nm) and single-mode CW operation with a maximum power of 6.4 mW at room temperature are demonstrated.

Ojanen et al. (2023), Lasers & Photonics Reviews

In this work, we demonstrate complementary metal-oxide-semiconductor (CMOS) compatible, rare-earth gain based large mode area (LMA) passively Q-switched laser in a compact footprint. We demonstrate high on-chip output pulse energy of >150 nJ in single transverse fundamental mode in the eye-safe window (1.9 µm), with a slope efficiency ~ 40% in a footprint of ~9 mm2. The high energy pulse generation demonstrated in this work is comparable or in many cases exceeds Q-switched fiber lasers. This bodes well for field applications in medicine and space.

Singh et al. (2023)

The microchip OPO device, based on the third-order (χ(3)) nonlinearity in a silicon nitride microresonator, produces output signal and idler fields widely separated from each other in frequency ( > 150 THz), and exhibits a pump-to-idler conversion efficiency up to 29 % with a corresponding output idler power of > 18 mW on-chip. This methodology can be readily applied to existing silicon photonics platforms with heterogeneously-integrated pump lasers, enabling flexible coherent light generation across a broad range of wavelengths with high output power and efficiency.

Perez et al. (2023), Nature communications

A self-injection locked laser with narrow linewidth down to 345 Hz is presented here, which is composed of distributed feedback (DFB) semiconductor laser and high quality (Q) factor silicon nitride (SiN) external cavity, with tunable sagnac loop reflector on the basis of add-drop type high Q microring resonator (MRR).

Su et al. (2022), SPIE digital library

We exploit the low-loss features of Si3N4 waveguides and demonstrate a hybrid laser comprising a GaSb gain chip with an integrated tunable Si3N4 Vernier mirror. At room temperature, the laser exhibited a maximum output power of 15 mW and a tuning range of 80 nm (1937 – 2017 nm).

Zia et al. (2022), Optics Letters

Guo et al. (2022), IEEE Xplore

Liu et al. (2022), IEEE Xplore

A hybrid InP/SiN tunable laser based on microring resonators exhibiting 40mW fibercoupled output power and 5kHz linewidth is demonstrated.

Calò et al. (2022)

We generate a quantum light source of eight pairs of correlated photons in a wavelength range of 25.6 nm within telecom wavelength using a SiN micro-ring with an FSR of 200 GHz.

Fan et al. (2022)

This paper demonstrates a widely tunable III-V/Si3N4 hybrid-integrated external cavity laser with maximum output power 34 mW, 2.5 kHz intrinsic linewidth, a relatively faster switching time ~ 60 μs, and side mode suppression ratio more than 70 dB over the tuning range of 58.5 nm. The external feedback circuit is based on 800-nm-thick Si3N4 waveguides with an optical confinement factor of 87%.

Guo et al., IEEE Xplore (2021)

We demonstrate an adaptable method for ultrastable control of low-energy femtosecond pulses based on common electro-optic modulation of a continuous-wave laser light source – the electro-optic modulation of a continuous-wave laser light source can also generate optical frequency combs.

Carlson et al., Science (2018)

This paper introduces a groundbreaking approach to solid-state LiDAR by integrating a single soliton microcomb with an optical phased array (OPA). This innovative architecture replaces conventional multi-laser systems with a single laser that pumps a microcomb, generating numerous wavelength channels for parallel sensing. To achieve precise beam steering with a wide field of view and minimal divergence, the system employs an ultra-long optical grating antenna that capitalizes on the bound state in the continuum (BIC) effect. By combining microcombs with OPAs, we enable high-speed, high-resolution 3D imaging while significantly reducing system complexity and cost. Experimental results showcase enhanced beam quality and improved distance measurement stability, paving the way for fully integrated, high-frame-rate, all-solid-state LiDAR systems ideally suited for demanding applications such as autonomous driving and aerial sensing.

Jingye Chen et al. (2025), Nature Communications

Optical phased arrays (OPAs) offer a promising solution for integrating beam focusing and steering functionalities on a chip. In this work, we present a 32-antenna OPA fully integrated on a commercially available silicon nitride (SiN) platform, operating in the wavelength range of 1500 nm to 1630 nm. We detail the design of the circuit and its components, emphasizing the development of a highly efficient phase shifter that requires 130 mW for a 2π phase shift. Testing the fabricated and assembled chip demonstrates a field of view of 24.28∘× 9.4∘ and a beam resolution of 0.66∘ × 0.082∘. To the best of our knowledge, these values are the highest reported for a fully SiN-based OPA at 1550 nm.

Saeed Arsanjani et al. (2024), Optics Express

Optical ranging is a crucial technology in metrology, with dual-comb systems offering high precision and fast acquisition rates. Traditional dual-comb ranging systems using microcombs face limitations due to short ambiguity distances, the need for high-bandwidth detectors, and complex stabilization controls. This study demonstrates that coherent Kerr soliton microcombs, generated from a shared light source, overcome these limitations by enhancing coherence and compatibility with low-bandwidth detectors, thereby simplifying system controls. The use of coherent microcombs extends the ambiguity distance from approximately 1.5 mm to 3.28 m through the Vernier effect, with an uncertainty of about 1.05 × 10⁻⁷. Additionally, the approach significantly reduces computational costs, enabling real-time processing and making it suitable for applications such as industrial process monitoring when combined with specialized FPGA technology.

Yuechen Yang et al. (2024), Journal of Lightwave Technology

In this study, a III/V-Si3N4 hybrid-integrated external cavity laser (ECL) is used to generate an FMCW signal over a large wavelength tuning range of 68 nm. The maximum output optical power is 15.8 mW, and the intrinsic linewidth is 0.9 kHz. By modulating the phase shifter, an FMCW signal with a chirp bandwidth of 0.7 GHz is generated at a repetition rate of 1 kHz. The pre-distortion algorithm is combined with the gain-tunable EO-PLL system to suppress the chirp nonlinearity and frequency noise across multiple wavelengths, leading to a remarkable improvement in range precision from 202 to 4.2 cm when targeting a distance of 200 m.

Liu et al. (2024), Laser & Photonics Review

This study proposes a solid-state two-dimensional beam-steering device based on an electro-optical phased array (EOPA) in thin-film lithium niobate (TFLN) and silicon nitride (SiN) hybrid platforms, thereby eliminating the requirement for the direct etching of TFLN. Electro-optic (EO) phase modulator array comprises cascaded multimode interference couplers with an SiN strip-loaded TFLN configuration, which is designed and fabricated via i-line photolithography. Each EO modulator element with an interaction region length of 1.56 cm consumed a minimum power of 3.2 pJ/π under a half-wave voltage of 3.64 V and had an estimated modulation speed of 1.2 GHz. Subsequently, an SiN dispersive antenna with a waveguide grating was tethered to the modulator array to form an EOPA, facilitating the out-of-plane radiation of highly defined near-infrared beams. A prepared EOPA utilized EO phase control and wavelength tuning near 1550 nm to achieve a field-of-view of 22° × 5° in the horizontal and vertical directions. The proposed hybrid integrated platform can potentially facilitate low-power and high-speed beam steering.

Lee et al. (2023), Optics Express

In this work, we propose and experimentally demonstrate such an On-chip optical delay lines (ODLs) based on chirped waveguide Bragg gratings (CWBG). This device is fabricated on a low-loss 800-nm-height silicon nitride platform, combining 20.11-cm long index-chirped multi-mode spiral waveguide antisymmetric Bragg gratings with a directional coupler. The bandwidth of this circulator-free ODL is 23 nm. The total GD is 2864 ps and the delay-bandwidth product is 65.87 ns·nm, which both are the largest values achieved by on-chip CWBG reported to our knowledge.

Li et al. (2023), Optics Express

This study proposes and demonstrates a dispersive silicon–nitride OPA that allows for passive wavelength-tuned steering of a line beam with an elongated vertical beamwidth.

Bhandari et al. (2022), Scientific Reports

A 56 nm wavelength tuning range, 2.9 kHz linewidth, maximum output power 22.5 mW, and static frequency step bandwidth 56 GHz hybrid integrated external cavity laser is reported based on silicon nitride vernier microring resonators functioning as an optical bandpass filter. A frequency-modulated continuous-wave (FMCW) signal is generated under synchronous modulation with a chirp bandwidth of 7.68 GHz at a 1 kHz repetition rate.

Liu et al. (2022), IEEE Xplore

We fabricated in silicon nitride technology a proof of concept steerer with beam waist 0.36° ×0.175°, addressing a field of view of 15° ×2.8°. A new design iteration is also reported with and 0.24° ×0.16° beam waist and 15° ×11.2° field of view.

Munoz et al. (2022), IEEE Xplore

We propose and demonstrate an optical phased-array-based bidirectional grating antenna (BDGA) in silicon nitride waveguides. The manufactured BDGA could achieve an enhanced beam-steering efficiency of 0.148 deg/nm as well as a stable spectral emission response in the wavelength range of 1530–1600 nm.

Lee et al., Photonics Research (2022)

We present a hybrid integrated SiN-polymer OPA for realizing an efficient LiDAR. The polymeric modulators are integrated with a SiN power splitter and grating antenna.

Im et al., IEEE Xplore (2021)

Jha et al. (2021)

We propose and demonstrate a backward-emitting silicon nitride optical phased arrays (OPA) incorporating a reinforced grating vector, which provides efficient wavelength-tuned beam steering along the longitudinal direction.

Im et al., IEEE Xplore (2020)

This paper investigates advanced nonlinear pulse dynamics in integrated photonics, demonstrating how matching the group velocity between ultra-short pulses in orthogonally polarized fundamental modes can drastically enhance supercontinuum generation via intermodal cross-phase modulation (iXPM). By precisely engineering a multi-mode silicon nitride channel to maximize the temporal overlap of a higher-order soliton and a 30 nm bandwidth probe pulse, the researchers successfully converted 25 percent of the input photons at 1230 nm into a phase-matched dispersive wave near the visible spectrum at 650 nm. This achievement represents a two-orders-of-magnitude increase in conversion efficiency over unmatched setups, providing a robust framework for shaping high-efficiency, multi-octave light sources for precision optical metrology and biomedical imaging.

Timmerkamp et al. (2026), Optics Express

This article demonstrates that single-channel wireless transmission at 112 Gbps is achievable at 560 GHz — well above the congested 300 GHz band targeted by current 5G infrastructure — by using a silicon nitride soliton microcomb as a compact, low-phase-noise optical frequency reference for photonic THz generation. Researchers at Tokushima University phase-locked two distributed-feedback lasers to adjacent comb lines and photomixed them to generate a stable 560 GHz carrier, achieving HD-FEC-qualified 16QAM transmission at 28 GBaud and setting a new benchmark for photonic wireless links beyond 350 GHz. LIGENTEC’s role is direct and hardware-critical: the SiN ring microresonator at the heart of the system — with a 560 GHz free spectral range and Q factor of approximately 10⁶ — was custom-fabricated by LIGENTEC S.A., demonstrating how the company’s ultra-low-loss silicon nitride platform enables not only photonic integrated circuits for datacom and sensing, but also frontier research in sub-terahertz wireless communications and next-generation 6G backhaul infrastructure.

Tokizane et al. (2026), Nature Communications Engineering

This paper presents a cavity-less approach for high-power integrated optical frequency combs using non-degenerate cascaded four-wave mixing in dispersion-engineered silicon nitride waveguides — bypassing traditional microcavities to eliminate their inherent constraints on efficiency, line-spacing tunability, and per-line power. The waveguide design at the heart of the system was fabricated at the LIGENTEC foundry, with a dual-oscillator power amplifier seed source delivering the quasi-CW tones required to drive the on-chip nonlinear process. At its optimal operating point, the cavity-less comb generates 283 lines across a 623 nm span, achieves 79% pump-to-comb conversion efficiency, and offers continuous line-spacing tunability over a 627 GHz range. Phase-resolved characterisation confirms high mutual coherence and transform-limited ultrafast soliton pulses — well suited for power-hungry applications including AI accelerators and coherent communications.

Roy et al. (2026), arXiv Physics Optics

This article demonstrates a compact, hybrid-dispersion photonic spectrograph that achieves a high resolving power exceeding 25,000 and a broad bandwidth of over 180 nm by integrating a cascaded phase-modulation silicon nitride waveguide-array chip with an orthogonal free-space dispersion module. Occupying a footprint on the order of cubic centimeters—three orders of magnitude smaller than traditional meter-scale instruments—this architecture effectively decouples resolution and bandwidth to overcome fundamental design trade-offs. The system was validated through successful wavelength and flux calibrations, acetylene absorption measurements, and the first reported detection of near-infrared solar Fraunhofer lines (Fe I at 1564.85 nm and 1565.29 nm) using an integrated spectrograph. While currently limited by single-mode fiber feeding and polarization sensitivity, the device’s inherent scalability and wafer-level replicability provide a promising integrated solution for future large-scale spectroscopic surveys, massively parallel astronomical instrumentation, and space-based applications.

Zang et al. (2026), Nature Photonics

Xia et al. (2026), Optics Express

This article investigates multi-timescale frequency–phase matching in coupled silicon-nitride microring lattices, revealing how engineered fast and slow photonic timescales enable robust, high-yield generation of multiple optical harmonics across broad pump powers and wavelengths. Through comprehensive fabrication, characterization, spatial imaging, and simulations, we demonstrate that nested frequency combs and multi-harmonic processes emerge even under relaxed phase-matching conditions—a stark contrast to the stringent requirements and low yields of single-ring systems. These results establish a versatile, scalable photonic platform that passively supports broadband nonlinear interactions, opening new opportunities for integrated quantum light sources, frequency conversion, and advanced spatiotemporal photonic control.

Mehrabad et al. (2025), Science

This article discusses the development and potential applications of a silicon-nitride photonic integrated waveguide designed for dual-polarization four-wave mixing, highlighting its advantages in optical communication systems by demonstrating a single silicon nitride (SiN) waveguide capable of supporting both transverse-electric (TE) and transverse-magnetic (TM) modes for polarization-independent functionality. The research details the waveguide design for optimal four-wave mixing (FWM) at 1550 nm, showcasing successful wavelength conversion with a 20 nm bandwidth and high-speed 25-Gbaud (50-Gb/s) quadrature-phase-shift-keyed (QPSK) signal demodulation with bit-error rates (BERs) below the forward-error-correction (FEC) threshold, ultimately paving the way for compact and efficient polarization-diversity coherent optical communication systems.

Ishimura et al. (2025), Optics Express

This paper demonstrates the self-organization of a spatiotemporal quasi-phase-matching (QPM) grating in silicon nitride microresonators[cite: 4, 5]. This grating, which involves the simultaneous spatial and temporal modulation of the nonlinear response, emerges through all-optical poling[cite: 4, 5]. The process is mediated by the coherent photogalvanic effect, leading to the formation of a traveling space-charge grating[cite: 5]. This grating affects both momentum and energy conservation, resulting in a quasi-phase-matched second harmonic that exhibits a Doppler shift[cite: 5]. The observation of this photoinduced spatiotemporal QPM broadens the understanding of phase matching conditions in nonlinear photonics[cite: 6].

Zhou et al. (2025), Nature Communications

This research investigates Second Harmonic Generation (SHG) in silicon nitride (SiN) waveguides integrated with MoS2 monolayers. By accounting for the full vectorial nature of the electromagnetic fields and the tensorial properties of MoS2’s susceptibility, researchers observed unexpected SHG enhancements, even when the primary electric field component was orthogonal to the MoS2 plane. This study highlights the crucial role of these factors in optimizing SHG efficiency. The findings provide valuable guidelines for designing on-chip photonic devices integrated with 2D materials for various nonlinear optical applications.

Rehan et al. (2024), arXiv physics optics

This paper presents the development of a novel photonic device for ultrabroadband resonant frequency doubling, leveraging two independent microring resonators with a shared interaction region. This design allows the resonant enhancement of both the pump and second harmonic to be tuned separately, overcoming traditional bandwidth and phase-matching limitations. Utilizing silicon nitride integrated photonics and photoinduced quasi-phase matching, the device demonstrates efficient second-harmonic generation across a broad telecom band, with applications in frequency comb upconversion and coherent light bridging. The approach provides scalable, reconfigurable, and high-power nonlinear optical functionalities on a chip.

Clementir et al. (2024), arXiv

Here we demonstrate a miniaturized optical frequency division system that can potentially transfer the approach to a complementary metal-oxide-semiconductor-compatible integrated photonic platform. Phase stability is provided by a large mode volume, planar-waveguide-based optical reference coil cavity and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator. Besides achieving record-low phase noise for integrated photonic mmWave oscillators, these devices can be heterogeneously integrated with semiconductor lasers, amplifiers and photodiodes, holding the potential of large-volume, low-cost manufacturing for fundamental and mass-market applications.

Sun et al. (2024), Nature

Here, we demonstrate an ultra-low phase noise mmWave oscillator by leveraging integrated photonic components and Kerr optical frequency division. The oscillator derives its stability from an integrated CMOS-compatible SiN coil cavity, and the optical frequency division is achieved spontaneously through Kerr interaction between the injected reference lasers and soliton microcombs in the integrated SiN microresonator. Besides achieving record-low phase noise for integrated mmWave oscillators, our demonstration greatly simplifies the implementation of integrated OFD oscillators and could be useful in applications of Radar, spectroscopy, and astronomy

Sun et al. (2024), arXiv

Here, we investigate the factors that could influence the phase noise of microwave signals generated with dual-pumped soliton microcombs, including the polarization, amplitude noise, and phase noise of the two pumps. We demonstrate a 25.25 (12.63) GHz microwave with phase noise reaching −112(−118) dBc/Hz at a 10 kHz offset frequency, surpassing the performance of previous reports on microwave generation using free-running Si3N4 soliton microcombs, even those generated with higher Q microresonators.

Liu et al. (2024), Optics Letters

This study investigates the thermal compensation mechanism in dual-mode Si3N4 microresonators that demonstrates the ease of generation of single-solitons with nearly octave-wide spectral bandwidth. Interestingly, these dual-mode resonators also support the coexistence of primary combs and solitons, enabling their utilization as functional microwave synthesizers. Furthermore, these resonators readily facilitate the generation of diverse multi-solitons and soliton crystals.

Weng et al. (2024), Optics Express

In this work, we demonstrate electro-optical modulation in a silicon nitride microring resonator enabled by electric-field poling, eliminating the complexities associated with material integration and providing data modulation speeds up to 75 Mb/s, currently only limited by the electrode design. With an estimated inscribed electric field of 100 V/μm, we achieve an effective second-order susceptibility of 0.45 pm/V. In addition, we derive and confirm the value of the material’s third-order susceptibility, which is responsible for the emergence of second-order nonlinearity. These findings broaden the functionality of silicon nitride as a platform for electro-optic modulation.

Zabelich et al. (2024), APL Photonics

This study presents a novel approach to wireless data transmission at 560 GHz, leveraging the use of THz waves generated through the injection-locking of a pair of distributed feedback lasers into a Kerr micro-resonator soliton comb. This innovative approach holds promise for achieving high-quality, high-speed wireless data transmission, thereby advancing THz communication technology for integration into 6G systems. The work is based on the Si3N4 taped out by LIGENTEC.

Tokizane et al. (2024), Optics Continuum

Here, we demonstrate that the Kerr nonlinearity enables passive, electronics-free synchronization of a microresonator-based dissipative Kerr soliton (DKS) optical-frequency comb (OFC) to an externally injected reference laser. The KIS-mediated enhancements we demonstrate can be directly implemented in integrated optical clocks and chip-scale low-noise microwave generators. The work is based on the Si3N4 taped out by LIGENTEC.

Moille et al. (2023), Nature

The demand for higher data rates in next-generation mobile wireless communication
systems (6G) has led to significant interest in terahertz (THz) waves as a highfrequency, broad modulation bandwidth carrier wave. In this study, we propose and demonstrate a wireless data transfer in the 560-GHz band using low-phase-noise THz waves generated by photomixing of a pair of distributed feedback lasers injectionlocking to Kerr micro-resonator soliton comb.

Tokizane et al. (2023), Arxiv

We present the dispersion engineering of a three-microring photonic molecule via thermo-optic effects. Despite the overall normal GVD, local regimes of normal and anomalous dispersion are tailored by fine-tuning the microcavities’ supermode frequencies.

Trinchão et al. (2023), CLEO 2023 conference contribution

Optically generated terahertz (THz) oscillators have garnered considerable attention in recent years due to their potential for wide tunability and low phase noise. Here, for the first time, a dissipative Kerr microresonator soliton comb (DKS), which is inherently in a low noise state, is utilized to produce a stepped-frequency THz signal (≈ 280 GHz).

Nawwar et al. (2023), Arxiv

We present the concept and design of a 100 GHz PIC-based nonlinear frequency division multiplexed transmission system in which four b-modulated spectrally overlapping channels are spectrally stitched without frequency guard bands to obtain a continuous spectrum.

Moscoso-Mártir et al. (2023), Science Direct

We demonstrate degenerate optical parametric oscillation in a triple-state silicon nitride photonic molecule. DOPO is generated with a phase-coherent dual-tone pump scheme, and the phase-matching conditions are optimized by tuning the resonances with microheaters.

Tomazio et al. (2023), CLEO 2023 conference contribution

We demonstrate a miniaturized optical frequency division system that can pgenerate microwaves with superior spectral purity on a CMOS-compatible integrated photonic platform. Phase stability is provided by a large-modevolume, planar-waveguide-based optical reference coil cavity and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator. Record-low phase noise is achieved, and its heterogeneous integration with lasers, amplifiers and photodiodes holds vast application potential.

Sun et al. (2023)

We introduce nonlinear networks—systems of nonlinear photonic elements that observe a programmable set of conservation rules, and highlight their diverse capabilities by demonstrating an optical frequency synthesizer, which operates at nearly arbitrary output frequency exceeding the state of the art in synthesized conversion bandwidth. Using a codesigned microresonator network, our synthesizer is based on four-wave mixing (FWM) spectral translation of a tunable laser and a frequency comb from a silicon nitride chip.

Black et al. (2023), Physical Review

Here, we report broadly tunable milliwatt-level second-harmonic generation in a small free spectral range silicon nitride microresonator, where the pump and its second-harmonic are both always on the fundamental mode. By carefully engineering the light coupling region between the bus and microresonator, we simultaneously achieve critical coupling of the pump as well as efficient extraction of second-harmonic light from the cavity. Thermal tuning of second-harmonic generation is demonstrated with an integrated heater in a frequency grid of 47 GHz over a 10 nm band.

Nitiss et al. (2023), Optics Express

We demonstrate that the all-optical inscription of second-order nonlinearity through the coherent photogalvanic effect allows not only degenerate but also non-degenerate sum-frequency generation in silicon nitride waveguides. Several multiphoton absorption processes can occur simultaneously, such that their quantum interference allows for the inscription of distinct charge gratings for quasi-phase matching of several second-order nonlinear processes within the same waveguide.

Yakar et al. (2023), SPIE digital library

For the first time, we report integrated firstorder quasi-phase-matched backward second-harmonic generation (BSHG) enabled by seeded all-optical poling. We carried out the demonstration in an integrated Si3N4 waveguide buried in SiO2 fabricated by LIGENTEC SA using its AN800 platform.

Yakar et al. (2023)

The non-degenerate sum-frequency generation quasi-phase-matching gratings are reported on a silicon nitride chip, and supports the theory of coherent photogalvanic effect with time dynamics analysis

Yakar et al. (2022), Laser & Photonics Reviews

A quantum light source of eight pairs of correlated photons in a wavelength range of 25.6 nm within telecom wavelength using a SiN micro-ring with an FSR of 200 GHz.

Fan et al. (2022)

Based on the third-order (χ(3)) nonlinearity in a silicon nitride microresonator, an OPO device produces output signal and idler fields widely separated from each other in frequency (>150 THz), and exhibits a pump-to-idler conversion efficiency up to 29 % with a corresponding output idler power of >18 mW on-chip.

Perez et al. (2022)

CW-driven dissipative Kerr solitons in a high-Q standing-wave (intrinsic Q ~ 4 million) Fabry-Perot microresonator on a silicon nitride chip with an FSR ~ 19 GHz.

Wildi et al. (2022)

This paper thoroughly presents the design strategy to reliably attain an ultra-wide soliton microcomb with dual-modes separated by ∼10 GHz in the silicon nitride (Si3N4) platform.

Weng et al. (2022), APL Photonics

Huang et al. (2022)

Through sign-alternating the dispersion in a CMOS compatible silicon nitride waveguide, we present a scheme to get up to 1000 nm bandwidth Supercontinuum Generation, achieve an efficiency enhancement factor of 2800, and lower the pulse energy requirement from nanojoules to 6 picojoules.

Zia et al. (2022)

We implement thermally assisted electric-field poling, which allows charge carrier separation in the waveguide core and results in an effective second-order susceptibility (χ(2)) inside the Si3N4 waveguide, making linear electro-optic modulation accessible on the platform for the first time.

Zabelich et al. (2022), ACS Photonics

We examine theoretically and experimentally the nonlinear coupling mechanism in a 1 THz repetition rate silicon nitride resonator and demonstrate four-wave mixing Bragg scattering between the different wavepackets forming the multi-color soliton, with the microcomb ranging over 150 THz, yielding a complex all-optical and integrated synthetic frequency lattice.

Moille et al. (2022)

We present optically reconfigurable quasi-phase-matching in large-radius silicon nitride microresonators, resulting in up to 12.5-mW on-chip second-harmonic generated power and a conversion efficiency of 47.6% W−1.

Nitiss et al., Nature Photonics (2022)

We demonstrate a photonic molecule composed of two coupled microring resonators on an integrated nanophotonic silicon nitride chip, designed to generate strongly squeezed light uncontaminated by noise from unwanted parasitic nonlinear processes.

Zhang et al., Nature Communications (2021)

We experimentally demonstrate the optical frequency division of an optically carried 3.6 THz reference down to 300 GHz through a dissipative Kerr soliton.

Tetsumoto et al., Nature Photonics (2021)

We report the generation of broadband single-mode (degenerate) quadrature squeezed vacuum from an integrated nanophotonic device based on two coupled silicon nitride microring resonators.

Zhang et al., scienceOPEN (2020)

We demonstrate a highly tunable second-harmonic generation in a silicon nitride integrated photonic platform.

Nitiss et al., Optics Letters (2020)

We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators.

Vaidya et al. (2019)

We experimentally demonstrate stimulated four-wave mixing in two linearly uncoupled integrated Si3N4 micro-resonators.

Tan et al. (2019)

We describe research on an optical-frequency synthesizer in a low-power chip-scale package that provides a laser output with a programmable optical frequency across 50 nm of bandwidth centered at 1550 nm, with a resolution smaller than one part in 10^14. Optical synthesizer is composed of a heterogeneously integrated III-V/Si tunable laser, which is guided by dual dissipative-Kerrsoliton frequency combs fabricated on separate silicon chips and pumped by off-chip laser.

Bowers et al. (2019)

We use a heterogeneously integrated III–V/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon nitride chips and pumped by off-chip lasers. With this tunable-laser and frequency-comb system, we demonstrate synthesis across a 4-THz segment of the C-band with 1 Hz resolution. Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here.

Spencer et al., Nature (2018)

Here we show that quasi-phase-matching via periodic modulations of the waveguide structure on a silicon nitride photonic chip provides a useful mechanism to control the evolution of ultrafast pulses during supercontinuum generation.

Hickstein et al., Physical Review Letters (2017)

This paper presents a deterministic and reconfigurable method for generating micro-resonator soliton crystals that serve as powerful, multi-wavelength optical sources for intensity-modulated direct-detection data transmission. By symmetrically positioning a pump and auxiliary laser around an avoided-mode-crossing resonance, the authors achieve reliable, repeatable access to specific soliton-crystal orders (ranging from 2-SC to 7-SC). This approach enables controlled comb-line spacing and delivers significantly enhanced comb-line power—up to 22.8 dB higher than single-soliton states. Using these bright, high-power comb lines from a CMOS-compatible silicon-nitride platform, the team demonstrates 46-GBd PAM4 data transmission across seven wavelengths in the C-band, achieving bit-error rates near 10⁻⁵ over 4 km of fiber. The work further shows how “imperfect” soliton crystals help mitigate auxiliary-laser-induced noise and expand the number of usable channels. Overall, this study establishes a robust, tunable microcomb approach that is well-suited for cost-efficient, high-capacity data-center interconnects.

Kenny Y.K.Ong et al. (2025), Laser & Photonics Reviews

This article presents a novel method for generating high-power, thermally accessible dissipative Kerr solitons in silicon nitride microresonators. The researchers designed an optimized microresonator structure and developed a robust pump-tuning scheme that enhances thermal accessibility, enabling deterministic single-soliton generation without the need for complex thermal compensation or fast tuning. By operating in the over-coupled regime and tailoring dispersion, the system achieves up to 50 mW output power and nearly 30% conversion efficiency—significantly higher than conventional approaches. The method, validated through 80 consecutive successful trials, demonstrates a stable and automated pathway to octave-spanning single solitons, advancing the practical use of microcomb technology in real-world applications such as optical communications, frequency metrology, and precision timing systems.

Andreas Jacobsen et al. (2025), Photonics Research

This study presents a novel approach for octave-spanning Kerr soliton generation in silicon nitride microresonators using integrated heaters for precise dual-mode thermal control. Soliton generation is optimized by electrically tuning mode separation, improving the yield of dual-mode resonators. Deterministic soliton generation is achieved by adjusting heater voltage (slow sweep or fast pulse) without changing the pump wavelength, simplifying the system. Robust octave-spanning soliton frequency combs with ~1 THz and 390 GHz repetition rates were demonstrated across multiple resonators. Bidirectional voltage tuning enables smooth transitions between multisoliton and single-soliton states, optimizing bandwidth and power. The integrated heater also allows precise fine-tuning of repetition rate and carrier-envelope offset frequency. These improvements significantly enhance the stability and yield of octave-spanning Kerr frequency combs, enabling their use in optical clocks and frequency synthesizers.

Haizhong Weng et al. (2024), Physical Review Applied

This study explores the efficacy of various chaotic microcomb spectra in optical coherence tomography (OCT) imaging, highlighting the advantages of a 95 GHz laser microcomb for achieving high-resolution tomograms with optimal imaging depth. The authors compare the chaotic comb state with dispersive Kerr solitons, emphasizing the trade-offs between spectral bandwidth and noise fluctuations. Using advanced post-processing techniques, including phase corrections and multi-scan averaging, they enhance image clarity and reduce artifacts in the acquired OCT images of diverse samples, such as a tape stack, pig retina, and strawberry. Their findings demonstrate that while chaotic microcombs introduce some intensity noise, the use of multiple scans can mitigate these effects, yielding results comparable to those obtained with standard light sources.

T.Melton et al. (2024), APL Photonics

Here, we report a dual-comb–based coherently parallel DAS concept, enabling linear superposition of sensing signals scaling with the comb-line number to result in unprecedented sensitivity enhancement, straightforward fading suppression, and high-power Brillouin-free transmission that can extend the detection distance considerably. The dual-comb here is generated from the SiN PICs fabricated by Ligentec.

Li et al. (2024), Sciences Advances

Here, we demonstrate full phase-stabilization of a selfinjection locked microcomb. The microresonator is implemented in a silicon nitride photonic chip and by controlling a pump laser diode and a microheater with low voltage signals (sub 1.5 V), we achieve independent actuators for the comb’s offset and line spacing frequencies. Both actuators reach a bandwidth of over 100 kHz and permit phase-locking to external frequency references. This establishes compact, electrically-driven photonic chip-based microcombs as scalable sources with low complexity for coherent precision metrology in emerging applications.

Wildi et al. (2024)

Here, we investigate the factors that could influence the phase noise of microwave signals generated with dual-pumped soliton microcombs, including the polarization, amplitude noise, and phase noise of the two pumps. We demonstrate a 25.25 (12.63) GHz microwave with phase noise reaching −112(−118) dBc/Hz at a 10 kHz offset frequency, surpassing the performance of previous reports on microwave generation using free-running Si3N4 soliton microcombs, even those generated with higher Q microresonators.

Liu et al. (2024), Optics Letters

We present a fast measurement method by employing a coherent heterodyne detection to simultaneously characterize the detuning between resonator resonances and comb lines over a broad spectral range in a single sweep, from which dispersion of a hot resonator can be estimated. This method can further be extended to a simultaneous measurement of relative phases between the comb lines.

Shoda et al. (2024), Optics Continuum

We demonstrate full phase-stabilisation of a self-injection-locked microcomb. The microresonator is implemented in a silicon nitride photonic chip fabricated by Ligentec, and by controlling a pump laser diode and a microheater with low voltage signals (sub 1.5 V), we achieve independent actuation of the comb’s offset and line spacing frequencies.

Wildi et al. (2024)

Here, we demonstrate a broadband polarization-entangled quantum frequency comb by combining an integrated silicon-nitride microresonator with a Sagnac interferometer. With a free spectral range of about 99 GHz and a narrow linewidth of about 190 MHz, our source provides 22 polarization-entangled photon pairs with frequency covering the whole telecom C-band. The entanglement fidelities for all 22 pairs are above 81%, including 17 pairs with fidelities higher than 90%. Our demonstration paves the way for employing the polarization-entangled quantum frequency comb in quantum network using CMOS technology as well as standard dense wavelength division-multiplexing technology.

Wen et al. (2023), Physical Review Applied

Here, we demonstrate, for the first time, a broadband polarization-entangled quantum frequency comb by combining an integrated silicon nitride microresonator with a Sagnac interferometer. With a free spectral range of about 99 GHz and a narrow linewidth of about 190 MHz, our source provides 22 polarization entangled photons pairs with frequency covering the whole telecom C-band. The entanglement fidelities for all 22 pairs are above 81%, including 17 pairs with fidelities higher than 90%. Our demonstration paves the way for employing the polarization-entangled quantum frequency comb in quantum network using CMOS technology as well as standard dense wavelength division multiplexing technology.

Wen et al. (2023), Arxiv

The microresonator is optimized by tapered design with two waveguides of different widths. Through balancing the dispersion and loss, the bandwidth of microcombs is improved by 61.2% compared with the traditional one.

Tao et al. (2023), IEEE

We demonstrate a stabilization scheme for dissipative Kerr solitons in SiN-resonators achieving high comb stability and long-term operation. Measuring 10Hz level absolute Kerr comb line stability (at 1 second) close to the pump, resulting in kHz level stability in the spectral domain of NIR astronomical spectrographs.

Kordts et al. (2023), CLEO 2023 conference contribution

We demonstrate the first observation of optical frequency combs at the edge state of the Su-Schrieffer-Heeger model. We show soliton-induced edge-bulk interaction and edge-state hopping.

Tusnin et al. (2023), CLEO 2023 conference contribution

Dissipative Kerr solitons (DKSs) intrinsically exhibit two degrees of freedom through their group and phase rotation velocity. Periodic extraction of the DKS into a waveguide produces a pulse train and yields the resulting optical frequency comb’s repetition rate and carrier-envelope offset, respectively. Here, we demonstrate that it is possible to create a system with a single repetition rate but two different phase velocities by employing dual driving forces. In particular, we show that a multiple-pumped DKS on the silicon nitride chip may generate a two-dimensional frequency comb, where cascaded nonlinear mixing occurs in the phase velocity dimension as well as the conventional mode number dimension, and where the repetition rate in each dimension differs by orders of magnitude.

Moille et al. (2023)

Here, we provide a simple, robust, and universal solution to produce pulses with sufficient peak power to initiate nonlinear supercontinuum generation spanning hundreds of terahertz (THz) using off-the-shelf polarization-maintaining (PM) amplification and nonlinear fiber components. We show how to readily achieve pulses shorter than 60 fs at a repetition rate of 20 GHz and with peak powers in excess of 2 kW. The same technique can be applied to picosecond pulses at 10 GHz to demonstrate temporal compression by a factor of 9× yielding 50 fs pulses with peak power of 5.5 kW. These compressed pulses enable flat supercontinuum generation spanning more than 600 nm after propagation through multi-segment dispersion-tailored anomalous-dispersion highly nonlinear fiber (HNLF) or tantala waveguides. The same 10 GHz source can readily achieve an octave-spanning spectrum for self-referencing in dispersion-engineered silicon nitride waveguides.

Sekhar et al. (2023)

We demonstrate microresonators with programmable synthetic reflection which enables robust access to self-injection-locked microcombs operating exclusively in the single-soliton regime and with low threshold power.

Ulanov et al. (2023)

We demonstrate wireless communication in a 560-GHz band by using a photonic THz emitter based on photomixing of a 560-GHz-spacing soliton microcomb (using the SiN PIC of LIGENTEC) in a uni-travelling carrier photodiode together with a THz receiver of Schottky barrier diode. The on-off keying data transfer with 2-Gbit/s achieves a Q-factor of 3.4, thus, satisfying the limit of forward error correction.

Tokizane et al. (2023)

A THz (≈560 GHz) wave with a low phase noise is provided by a frequency-stabilized, dissipative Kerr microresonator soliton comb based on the SiN chips fabricated at LIGENTEC. The repetition frequency of the comb is stabilized to a long fiber in a two-wavelength delayed self-heterodyne interferometer, significantly reducing the phase noise of the THz wave. A measurement technique to characterize the phase noise of the THz wave beyond the limit of a frequency-multiplied microwave is also demonstrated, showing the superior phase noise of the THz wave to any other photonic THz oscillators (>300 GHz).

Kuse et al. (2022), Communications Physics

We experimentally demonstrate that multiple microcombs can coexist in monochromatically pumped Si3N4 microresonators.

Wu et al., Optics Letters (2022)

A soliton microcomb prototype with a microring of 75 GHz FSR on silicon nitride chip coupled to fiber array.

Xi et al. (2022)

In this paper, we investigate the switchability of dissipative cnoidal waves (DCWs) based on dual-coupled Si3N4 microresonators.

Wu et al., Optics Express (2021)

A dissipative Kerr-microresonator soliton comb is scanned by 70 GHz in 500µs, 50 GHz in 125µs, and 25 GHz in 50µs (= 500 THz/s). Furthermore, we propose and demonstrate a method to measure the frequency shift of all comb modes, in which an imbalanced Mach–Zehnder interferometer with two outputs with different wavelengths is used.

Kuse et al., Optics Letters (2021)

We propose an integrated photonics interposer to replace discrete components of microcomb based systems (microcombs, other nonlinear elements, lasers and photodetectors, etc) around 1550 nm by collecting, routing and interfacing octave-wide microcomb-based optical signals between photonic chiplets and heterogeneously integrated devices using silicon nitride photonics.

Rao et al., Light Science & Applications (2021)

By employing Pound–Drever–Hall locking and a microheater on the silicon nitride microresonator, we show continuous scanning of the soliton comb modes across nearly the full free-spectral range of the microresonator without losing soliton operation, while spectral features with a bandwidth as small as 5 MHz are resolved.

Kuse et al., Optics Letters (2020)

We report a comprehensive study of low-power, octave-bandwidth, single-soliton microresonator frequency combs in both the 1550 nm and 1064 nm bands, and get direct soliton generation with less than 40 mW of chip-coupled laser power utilizing fully integrated silicon nitride Kerr microresonators.

Briles et al. (2020)

A microphotonic astrocomb is demonstrated via temporal dissipative Kerr solitons in photonic-chip-based silicon nitride microresonators, directly providing a spurious-free spectrum of resolvable calibration lines.

Obrzud et al., Nature Photonics (2019)

A broadband visible (VIS) blue-to-red, 10 GHz repetition rate frequency comb is generated by combined spectral broadening and triple-sum-frequency generation in an on-chip silicon nitride waveguide.

Obrzud et al., Optics Letters (2019)

Manurkar et al., OSA Continuum (2018)

We demonstrate robust frequency-control strategies for near-infrared, octave-bandwidth soliton frequency combs created with nanofabricated silicon nitride ring resonators. The comb links wavelengths between 767 and 1556 nm from a 1064 nm pump laser, and the mode frequencies of the comb are spaced by 1 THz.

Yu et al., Physical Review Applied (2018)

We explore the creation of an octave-spanning, 15-GHz repetition-rate microcomb suitable for both f−2f self-referencing and optical-frequency comparisons across the near infrared. Efficient silicon-nitride waveguides provide a supercontinuum spanning 700 to 2100 nm, enabling both offset-frequency stabilization and optical-frequency measurements with >100 nW per mode.

Lamb et al., Physical Review Applied (2017)

Using a continuous wave–pumped, dispersion-engineered, integrated silicon nitride microresonator, we generated continuously circulating temporal dissipative Kerr solitons.

Brasch et al., Science (2016)

This article, titled “Heterogeneously Integrated Squeezed-Light Generation and Detection on a Single Photonic Chip” by Haoran Chen et al., presents a breakthrough in quantum photonics by fully integrating squeezed-light generation, routing, and balanced homodyne detection onto a single photonic integrated circuit. Fabricated using commercial foundry technology from LIGENTEC, the photonic chip leverages LIGENTEC’s low-loss, high-confinement silicon nitride (Si3N4) platform to form ultra-high-Q microcavities and passive routing circuits, which are then combined with heterogeneously integrated III-V photodiodes via die bonding. By leveraging the low linear optical propagation losses provided by LIGENTEC technology alongside on-chip balanced detection, the researchers successfully achieved over 3 dB of squeezed light across multiple quantum modes while maintaining extremely low internal circuit loss, establishing a highly scalable architecture for continuous-variable quantum computing and optical quantum sensing.

Chen et al., (2026), arXiv Quantum Physics

This paper experimentally demonstrates a quantum-secure Physical Unclonable Function built on a SiN programmable Mach-Zehnder interferometer mesh — fabricated by LIGENTEC on the AN800 Multi-Project Wafer run using the 200mm production line — whose unique physical signature emerges from uncontrollable waveguide variations during fabrication. By combining single-photon states with the integrated mesh, the researchers introduce a quantum readout protocol that leverages maximally mixed quantum states to conceal the underlying unitary transformation from passive eavesdroppers, while the no-cloning theorem prevents state copying. Monte Carlo analysis confirms exceptional authentication performance against both side-channel and cloning attacks, achieving equal error rates as low as 10⁻¹⁴ — highlighting the potential of quantum-secured silicon photonic integrated circuits for high-security hardware authentication applications.

Sarantoglou et al., (2026), arXiv Physics Optics

This paper presents a comprehensive study of an actively tunable, interferometrically coupled silicon nitride microring resonator (MRR) designed to optimize high-brightness quantum light sources for foundry-scale photonic circuits. By utilizing two thermally controlled phase shifters to dynamically adjust the ring-bus coupling and resonator phase, the authors demonstrate post-fabrication control over the quality factor (Q-factor) between 10⁵ and 10⁶. This reconfigurability allows for the precise tailoring of photon-pair brightness, source emission bandwidth, and coincidence-to-accidental ratios (CAR) across multiple frequency modes. Crucially, the study provides the first experimental demonstration that optimal coupling and emission characteristics vary across frequency modes due to dispersion effects—shifting toward the overcoupled regime as dispersion increases—rather than occurring strictly at critical coupling. By achieving a maximum on-chip pair generation rate of 334 kHz and relaxing lithographic precision requirements through adaptive tuning, this work establishes a scalable, high-yield approach for developing application-agnostic building blocks in integrated quantum photonics.

Heine et al., (2026), Nanophotonics

This paper experimentally demonstrates a network of two coupled photonic quantum memristors with crossed feedback, implemented on a silicon nitride integrated circuit and driven by a room-temperature single-photon source based on a silicon-vacancy (SiV) color center. By adaptively updating the transfer function of each memristor based on detection events from the other, the researchers observed enhanced non-Markovian dynamics, including bistability and topologically non-trivial self-intersecting hysteresis loops. These results establish integrated photonic memristors as scalable, nonlinear building blocks suitable for compact quantum neuromorphic and reservoir computing architectures.

Baldazzi et al., (2026), arXiv :2602.14736

Xanadu’s paper introduces Aurora, a modular photonic quantum computer built from 35 photonic chips that serves as a proof-of-concept scale model demonstrating all the essential building blocks for universal, fault-tolerant quantum computing. The machine integrates 84 squeezers and 36 photon-number-resolving detectors across rack-mounted modules connected by fiber-optic links, and was used to synthesize a cluster state spanning 86.4 billion modes over a continuous two-hour run, while also successfully demonstrating real-time error decoding and adaptive single-clock-cycle feedforward. Although Aurora is explicitly sub-performant — with optical losses roughly 20–30 times higher than what fault-tolerant operation requires — the work establishes that the photonic approach is genuinely modular and scalable, and the authors provide a detailed loss-tolerance analysis that maps out a clear hardware roadmap toward crossing the fault-tolerant threshold.

Rad et al., (2026), Nature

This paper presents a novel, passive technique for certifying frequency-bin entanglement over multi-mode channels using linear interferometry and time-resolved detection. By leveraging a high-brightness multi-resonator source integrated on a silicon nitride chip, the researchers recorded the first joint temporal intensity (JTI) of frequency-bin entangled photons, enabling arbitrary projective measurements without the need for active modulation. To maintain path indistinguishability over distorted multi-mode fiber links, they utilized field-widened interferometers, achieving a CHSH inequality violation of $|S|=2.32\pm0.05$ and a state fidelity of up to 91%. This resource-efficient architecture establishes a scalable path for deploying robust quantum communication in challenging environments, such as satellite-to-ground links.

Vinet et al., (2026), npj Quantum Information

This article investigates strong nanophotonic quantum squeezing exceeding 3.5 dB in a foundry-compatible Kerr microresonator, authored by Yichen Shen et al.. The researchers report a directly detected squeezing level of dB using foundry-fabricated silicon nitride () microrings, which corresponds to an inferred on-chip squeezing level of 10.2 dB. This achievement represents the highest level of squeezing directly detected from a microresonator and a significant improvement over previous continuous-wave nanophotonic squeezers. To ensure stability and repeatability, the team utilized a PID feedback loop to stabilize pump detuning and employed small-radius rings with a large free spectral range (450 GHz) to lower parametric oscillation thresholds and mitigate thermally induced noise. The results demonstrate that is a viable, CMOS-compatible, and scalable platform for robust quantum noise reduction, paving the way for advanced on-chip quantum sensing, metrology, and information processing.

Shen et al., (2025), Optica

This work presents an integrated photonic circuit that implements the swap test using linear optical components and qudits, represented by single photons in waveguides. By utilizing 23 spatial degrees of freedom, the circuit simplifies the setup, removing the need for non-linearity or post-selection. The device encodes two qubits and accurately estimates their scalar product, with a root mean square error below 0.05, advancing the development of QML-compatible photonic systems.

Baldazzi et al., (2023), IOPScience

Here, we demonstrate the storage and retrieval of the entangled state of two telecom photons generated from an integrated photonic chip. Combining the natural narrow linewidth of the entangled photons and long storage time of 167Er3+ ions, we achieve storage time of 1.936 μs, more than 387 times longer than in previous works.

Jiang et al., (2023), Nature Communications

Here a multi-wavelength quantum light source using a silicon nitride micro-ring with a free spectral range of 200 GHz is demonstrated. The generation of eight-wavelength-paired photon pairs is ensured in a wavelength range of 25.6 nm. These results, at room temperature and telecom wavelength, in a CMOS-compatible platform, represent an important step toward integrated quantum photonic devices, which pave the way for realizing a large-scale quantum network.

Fan et al., (2023), Laser & Photonics Review

Here, we demonstrate the storage and recall of the entangled state of two telecom photons generated from an integrated photonic chip based on silicon nitride. Combining the natural narrow linewidth of the entangled photons and long storage time of 167Er3+ ions, we achieve storage time of 400 ns, more than one order of magnitude longer than in previous works.

Jiang et al., (2022)

We demonstrate controlled-NOT (CNOT) operation of a silicon nitride photonic integrated circuit using path-entangled photon pairs from a silicon-photonic integrated circuit as logical inputs, and the CNOT gate is by combining several silicon-nitride Mach–Zehnder interferometers for a linear-optical quantum gate. The fully packaged photonic circuits with electrical wire bonding and optical fiber bonding measures the logical-basis fidelity of CNOT operation better than 81%.

Lee et al., Optics Communications (2022)

A quantum light source of eight pairs of correlated photons in a wavelength range of 25.6 nm within telecom wavelength using a SiN micro-ring with an FSR of 200 GHz.

Fan et al. (2022)

Here we introduce a full-stack hardware−software system for executing many-photon quantum circuit operations using integrated nanophotonics on a silicon nitride chip: a programmable chip, operating at room temperature and interfaced with a fully automated control system.

Arrazola et al., Nature (2021)

We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators.

Vaidya et al., arXiv (2019)

This article demonstrates a co-packaged, receiver-side photonic reservoir computing equalizer designed to mitigate signal impairments in high-speed optical links without the heavy power and cost burdens of conventional digital signal processing. By integrating a 16-node spatially multiplexed reservoir fabricated on a silicon nitride platform with an InP receiver front-end, the researchers achieved all-optical equalization across a broad range of conditions, including baudrates from 10 to 46 Gbaud and transmission distances up to 250 km. A key innovation of this work is its simultaneous flexibility; the fixed-topology hardware does not require physical reconfiguration for different scenarios and is adapted solely through the retraining of its linear readout layer using a hardware-in-the-loop optimization strategy. Experimental results showed the reservoir consistently outperformed standard digital equalizers by up to four orders of magnitude in bit error rate improvement, a finding further validated by simulations extending the performance to 100 Gbaud and 500 km.

Masaad et al. (2026), arXiv Physics Optics

This paper experimentally takes an important step towards wavelength division multiplexing in an integrated waveguide-based photonic reservoir computing platform by using a single set of readout weights for up to at least 3 ITU-T channels to efficiently scale the data bandwidth when processing a nonlinear signal equalization task on a 28 Gbps modulated on-off keying signal. Using multiple-wavelength training, we obtain bit error rates well below that of the forward error correction limit at high fiber input powers of 18 dBm, which result in high nonlinear distortion.

Gooskens et al. (2024), Scienfic reports

We present the design and experimental characterization of a silicon nitride pulse interleaver based on coupled resonator optical waveguide filters.

Zazzi et al. (2023), Optics Express

Highlights the capability of commercial SiN foundries to fabricate ultra-small (7.4 mm × 2 mm), high-resolution, high-throughput AWG spectrographs on a chip suitable for both ground- and space-based telescopes.

Gatkine et al. (2022)

A 8.75 × 3 mm silicon nitride chip with a square waveguide cross-section of 800 × 800 nm is used to fabricate a continuous-output, curved focal-plane photonic Arrayed Waveguide Grating (AWG) with a resolving power of 12,000, a free-spectral range of 18 nm, and a wide operational band of 1425-1650 nm, which allows a continuous sampling of the spectrum in high precision spectroscopy.

Gatkine et al. (2022), SPIE digital library

We discuss the design and demonstration of 4-channel coarse wavelength-division (de-)multiplexers based on cascaded Mach-Zehnder interferometer (MZI) lattice filters and arrayed waveguide gratings (AWG) on a 150 nm silicon nitride ( Si3N4 ) platform.

Stanley Cheung and Michael R.T Tan, Journal of Lightwave Technology (2020)

Low-loss, fabrication-tolerant Si3N4 CWDM lattice filters and AWGs are demonstrated for 990 – 1065nm bottom-emitting VCSELs. Channel separation of 25 nm, XT <; -35 dB and -20 dB are reported with temperature shift of 14.5 pm/°C.

Stanley Cheung and Michael R.T Tan, IEEE Xplore (2020)

This article details a novel, balanced plasmo-photonic Mach-Zehnder interferometer (MZI) refractive index sensor built on a Si₃N₄ platform. Unlike typical designs, this sensor incorporates identical aluminum plasmonic metal stripes on both the sensor and reference arms, a configuration intended to improve resilience to environmental noise by ensuring that external perturbations create a common-mode effect that is cancelled out. Experimental results demonstrate a high bulk sensitivity of up to 8801 nm/RIU and a significantly improved Limit-of-Detection (LoD) of 4.4 x 10⁻⁶ RIU. This LoD represents an order of magnitude improvement compared to a reference MZI sensor with a plasmonic stripe on only a single arm, which measured an LoD of 5 x 10⁻⁵ RIU, thereby showcasing the balanced design’s enhanced stability and noise rejection capabilities.

Simos et al., IEEE Photonics Journal (2025)

This paper presents a photonically driven on-chip millimeter wave (mmWave) source. The source is enabled by the heterogeneous integration of a high-speed InGaAs/InP photodiode and silicon nitride (Si3N4) microcavity solitons. The chip delivers mmWaves with -18 dBm of electrical power at a frequency of 98 GHz with kHz-class linewidth and low phase noise. This demonstrates a significant advancement in on-chip photonic mmWave source performance, offering a compact and scalable solution for future low-noise mmWave applications in communications and sensing technologies.

Gao et al., Optica Vol. 12, Issue 4, pp. 465-468 (2025)

We present a hybrid integrated SiN-polymer OPA for realizing an efficient LiDAR. The polymeric modulators are integrated with a SiN power splitter and grating antenna.

Im et al., IEEE (2021)

Microwave-frequency acousto-optic modulation is realized by exciting high-overtone bulk acoustic wave resonances (HBAR) in the photonic stack on a silicon nitride photonic integrated chip. A Si3N4-based optical isolator is demonstrated by spatiotemporal modulation, with over 17 dB isolation achieved.

Tian et al., Nature Communications (2020)

Here we demonstrate InGaAs/InP modified uni-traveling carrier photodiodes on Si3N4 waveguides with 20 nA dark current, 20 GHz bandwidth, and record-high external (internal) responsivities of 0.8 A/W (0.94 A/W) and 0.33 A/W (0.83 A/W) at 1550 nm and 1064 nm, respectively.

Yu et al., Optics Express (2020)

This work demonstrates a heterogeneous platform by bonding lithium niobate (LN) thin films onto a silicon nitride (Si3N4) waveguide layer on silicon.

Chang et al., Optics Letters (2017)

Highlights the capability of commercial SiN foundries to fabricate ultra-small (7.4 mm × 2 mm), high-resolution, high-throughput AWG spectrographs on a chip suitable for both ground- and space-based telescopes.

Gatkine et al. (2022)

A 8.75 × 3 mm silicon nitride chip with a square waveguide cross-section of 800 × 800 nm is used to fabricate a continuous-output, curved focal-plane photonic Arrayed Waveguide Grating (AWG) with a resolving power of 12,000, a free-spectral range of 18 nm, and a wide operational band of 1425-1650 nm, which allows a continuous sampling of the spectrum in high precision spectroscopy.

Gatkine et al. (2022), SPIE digital library

By employing Pound–Drever–Hall locking and a microheater on the silicon nitride microresonator, we show continuous scanning of the soliton comb modes across nearly the full free-spectral range of the microresonator without losing soliton operation, while spectral features with a bandwidth as small as 5 MHz are resolved.

Kuse et al., Optics Letters (2020)

We describe infrared RV spectroscopy at the 10 m Hobby–Eberly Telescope that leverages a 30 GHz electro-optic laser frequency comb with a nanophotonic supercontinuum to calibrate the Habitable Zone Planet Finder spectrograph. The frequency comb generation includes a silicon nitride chip (5  mm×3  mm) on which nanophotonic waveguides are patterned.

Metcalf et al., Optica (2019)

We demonstrate robust frequency-control strategies for near-infrared, octave-bandwidth soliton frequency combs created with nanofabricated silicon nitride ring resonators. The comb links wavelengths between 767 and 1556 nm from a 1064 nm pump laser, and the mode frequencies of the comb are spaced by 1 THz.

Yu et al., Physical Review Applied (2018)

This paper presents a significant advancement in hybrid integrated photonics by demonstrating a high-speed, high-efficiency ring-assisted Mach-Zehnder modulator built on a lithium tantalate-on-silicon nitride platform. Fabricated within the established dual-layer silicon nitride multi-project wafer process line by LIGENTEC, the device seamlessly integrates the strong electro-optic properties of lithium tantalate with low-loss passive silicon nitride waveguides. By utilizing a ring-assisted configuration to enhance the optical phase shift, the architecture drastically reduces the required drive voltage and device footprint compared to conventional layout designs. This work establishes a highly manufacturable, wafer-scale solution for high-performance optical modulators, offering a crucial building block for next-generation high-capacity telecommunications, microwave photonics, and optical computing networks.

Tong Lin et al. (2025), Advanced Photonic Nexus

In a significant advance for programmable photonics, researchers have demonstrated a versatile silicon nitride (Si3N4) microresonator capable of dynamic reconfiguration into three distinct topological states using only a single control knob. By integrating a tunable balanced Mach-Zehnder interferometer to govern mutual mode coupling between counterpropagating light, the device can seamlessly transition between Möbius-like, Fabry-Pérot, and microring resonator configurations. Beyond this architectural flexibility, the platform achieves polarization-diverse operation and reveals rich physical dynamics, most notably free spectral range (FSR) multiplication and the “photonic pinning” effect, where specific optical supermodes remain frequency-fixed despite external tuning. These findings, successfully modeled through coupled-mode theory and validated on a commercial foundry platform, establish a robust building block for high-density, multifunctional photonic systems-on-chip and the exploration of synthetic dimensions in topological physics.

Tong Lin et al. (2025), Advanced Photonic Nexus

This article by Arif Rahman and Shayan Mookherjea from the University of California, San Diego, along with researchers from LIGENTEC SA (Switzerland), reports the wafer-scale integration of thin-film lithium niobate (TFLN) electro-optic modulators with silicon nitride (SiN) photonic circuits on conventional silicon wafers. The researchers used a hybrid-mode design with low-temperature wafer bonding, etched air trenches to reduce RF losses, and a dual SiN layer architecture for seamless transitions between components.

The fabricated modulators achieved a half-wave voltage-length product of 3.8 V·cm, insertion loss of 4 dB, extinction ratios exceeding 35 dB, and bandwidths up to 110 GHz. This platform enables scalable, high-performance photonic integrated circuits for communications, sensing, and quantum technologies without requiring LN etching.

Rhaman et al. (2025), Journal of Lightwave Technology

This article introduced a novel plasmonic barium titanate (BTO)-on-silicon nitride (SiN) integrated photonics platform designed for high-speed electro-optic modulation in next-generation optical communications. By combining low-loss SiN passives with the strong Pockels effect of BTO and nanoscale plasmonics, the researchers demonstrated three distinct modulator types: a 256 GBd C-band Mach-Zehnder (MZ) modulator, a 224 GBd C-band IQ modulator, and a 200 GBd O-band racetrack (RT) modulator. These devices achieved record-breaking data rates, including 448 Gbit/s with the IQ modulator and 340 Gbit/s with the MZ modulator. The platform featured compact footprints as small as , electro-optical bandwidths up to 110 GHz, and high thermal stability. Furthermore, the study showed that high-speed performance can be maintained using simplified, energy-efficient digital signal processing (DSP) with only linear equalization, reaching symbol rates up to 196 GBd. This work positions the BTO-on-SiN platform as a scalable, high-performance solution for applications ranging from AI systems to Tbit/s long-haul and short-haul communication links.

Kohli et al. (2025), Nature – Light Sciences and Applications

This article details both experimental and simulation findings for a fully etched, C-band grating coupler (GC) fabricated on an 800 nm silicon nitride platform, engineered to significantly suppress backreflections. Backreflections are minimized by truncating the initial grating teeth, which deflect reflected light at an oblique angle and excite higher-order modes that are subsequently filtered out by the tapered waveguide. To mitigate the resulting phase front distortion and associated insertion losses, the authors implemented an adaptive redesign employing elliptical gratings with varying eccentricity. This optimization reduced excess insertion losses from 2.4 dB to below 1 dB. The final design achieves a waveguide-to-waveguide backreflection suppression exceeding 10 dB—consistently maintaining levels below −25 dB across a 65 nm bandwidth—while retaining fabrication simplicity through a single etch process. Experimental measurements demonstrate a peak coupling efficiency of −8.8 dB, with simulations indicating a potential improvement to −6.4 dB through optimized cladding layer thicknesses, representing a notable advancement in photonic integrated circuit design.

Ghannam et al. (2025), Optics Letters

This paper details the fabrication and performance of hybrid lithium niobate (LN) electro-optic modulators integrated with low-loss silicon nitride (SiN) waveguides on a silicon platform, achieving over 30 dB extinction ratio, a low half-wave voltage-length product of 3.8 V.cm, and a modulation bandwidth exceeding 110 GHz. By combining the strengths of LN’s electro-optic properties with SiN’s low-loss waveguides through a scalable fabrication process, this technology enables high-performance modulation while leveraging existing silicon microelectronics infrastructure for streamlined production.

Md Arifur Rahman et al. (2025), Arxiv Physics

This research introduces an inverse design methodology for optimizing wideband photonic integrated circuits (PICs), leveraging artificial gauge fields (AGFs). By employing a neural network-assisted approach, the researchers successfully designed and fabricated a directional coupler-based power splitter with tunable, arbitrary splitting ratios across a broad bandwidth. Furthermore, they demonstrated the design of a microring resonator exhibiting a highly stable extinction ratio (ER). Experimental results on a silicon-on-insulator (SOI) platform validated the efficacy of this approach, showcasing less than 0.9 dB variation in power splitting and a mere 1.6 dB ER variation over a 100-nm wavelength range. This study underscores the significant potential of AGF structures in enabling the development of high-performance, compact, and efficient photonic devices, paving the way for advancements in diverse optical applications.

Wang et al. (2024), Advanced Photonics Nexus

This paper introduces a highly energy efficient photonic Mach-Zehnder interferometer (MZI) on the silicon nitride (Si3N4) platform, featuring hybrid Si3N4-BaTiO3 (BTO) electro-optic phase shifters (PS) for photonic neural networks (PNNs). The experimental results of the fabricated devices reveal low power consumption of only 121 nW for a π phase shift, extinction ratio surpassing 27 dB, and exceptionally low Vπ×L of 2.52 Vmm for a 2.1 mm long PS with insertion losses of 4.65 dB. This value can go down to 0.95 dB with proper processing of the BTO layer for fine etching according to 3D-FDTD simulations. Furthermore, the MZIs demonstrate rapid rise/fall times below 20 ns for 5 MHz RF square pulse modulation. The low loss and power consumption renders the proposed technology highly suitable for reconfigurable weighting elements in large-scale multi-layer PNNs.

Chrysostomidis et al. (2025), Journal of Lightwave Technology

This paper introduces a pioneering method for achieving electro-optic (EO) modulation in stoichiometric silicon nitride (Si₃N₄) through optically-assisted poling to induce second-order nonlinearity. Traditional approaches have faced challenges in eliciting a linear EO effect in Si₃N₄ due to its inherent inversion symmetry and high bandgap. However, by utilizing visible light at 780 nm to excite and separate charge carriers within a microring resonator under a high electric field, the authors successfully establish a stable effective second-order nonlinearity of 1.2 pm/V. This innovative technique eliminates the need for high-temperature processing, streamlining fabrication and improving device stability. The resulting modulator achieves a bandwidth of 4 GHz, constrained by the resonator’s quality factor, effectively addressing a significant gap in Si₃N₄ photonic platforms and paving the way for the development of compact, monolithic EO modulators essential for high-density photonic integrated circuits.

Christian Lafforgue et al. (2024), arXiv

This study presents the successful achievement of electro-optical modulation in a silicon nitride microring resonator, employing thermally assisted electric-field poling. With an inscribed electric field of 100 V/μm within the silicon nitride waveguide, an effective second-order susceptibility of 0.45 pm/V is induced. Leveraging silicon nitride as the active material for electro-optic modulation, we determined the operational bandwidth of the device, constrained by the electrode design, to be 78 MHz. Furthermore, we demonstrate the capability of the device to modulate data at bitrates of up to 75 Mb/s. Our findings highlight the potential of linear electro-optical modulation in the silicon nitride integrated platform.

Zabelvich et al. (2024), SPIE Digital Library

Here, we present an innovative approach to photonics by introducing a compact and multi-mode structure. This approach significantly reduces the contact between the optical field and the rough sidewalls in the high-confinement Si3N4 waveguide. By incorporating modified Euler bends, and a weakly tapered gap directional coupler, adiabatic transmission with simultaneous ultra-low loss and compact size is achieved even in 7-µm wide waveguide. Results show that the intrinsic quality factor Qi of MRR is (6.8 ± 0.4) × 10e6 at the wavelength of 1550 nm, which is approximately four times higher than the previously reported by the same fabrication process. An ultra-low loss of 0.051 ± 0.003 dB/cm is achieved based on the standard LIGENTEC-AN800 technology.

Cui et al. (2024), Optics Express

In this work, we propose and experimentally demonstrate, for the first time, an on-chip circulator-free dispersion compensator based on silicon nitride (Si3N4) CWBG with large and linear group delay. This integrated device has great potential for diverse applications such as long-haul transmission links, pulse compression, and pulse shaping.

Li et al. (2023), SPIE digital library

We propose and demonstrate an ultralow-loss Si3N4 racetrack MRR by shaping the mode using a uniform multimode structure to reduce its overlap with the waveguide. The MRR is fabricated by the standard multi project wafer (MPW) foundry process. It consists of two multimode straight waveguides (MSWs) connected by two multimode waveguide bends (MWBs). In particular, the MWBs are based on modified Euler bends, and an MSW directional coupler is used to avoid higher-order mode excitation. In this way, although a multimode waveguide is used in the MRR, only the fundamental mode is excited and transmitted with ultralow loss.

Cui et al. (2023), IEEE

We report on apodized chirped Bragg gratings in a silicon nitride-on-insulator platform. Applications for this device include nonlinear photonics, specifically dispersion compensation in mode-locked lasers operating in the short-wave infrared wavelength band.

Sinobad et al. (2023), CLEO 2023 conference contribution