Publications using our technology

AN OPTICAL-FREQUENCY SYNTHESIZER USING INTEGRATED PHOTONICS

Optical-frequency synthesizers, which generate frequency-stable light from a single microwave-frequency reference, are revolutionizing ultrafast science and metrology, but their size, power requirement and cost need to be reduced if they are to be more widely used. Integrated-photonics microchips can be used in high-coherence applications, such as data transmission1, highly optimized physical sensors2 and harnessing quantum states3, to lower cost and increase efficiency and portability. Here we describe a method for synthesizing the absolute frequency of a lightwave signal, using integrated photonics to create a phase-coherent microwave-to-optical link. We use a heterogeneously integrated III–V/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon chips and pumped by off-chip lasers. The laser frequency output of our optical-frequency synthesizer can be programmed by a microwave clock across 4 terahertz near 1,550 nanometres (the telecommunications C-band) with 1 hertz resolution. Our measurements verify that the output of the synthesizer is exceptionally stable across this region (synthesis error of 7.7 × 10−15 or below). Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here. Leveraging high-volume semiconductor processing built around advanced materials could allow such low-cost, low-power and compact integrated-photonics devices to be widely used.

Daryl T. Spencer, Tara Drake, Travis C. Briles, Jordan Stone, Laura C. Sinclair, Connor Fredrick, Qing Li, Daron Westly, B. Robert Ilic, Aaron Bluestone, Nicolas Volet, Tin Komljenovic, Lin Chang, Seung Hoon Lee, Dong Yoon Oh, Myoung-Gyun Suh, Ki Youl Yang, Martin H. P. Pfeiffer, Tobias J. Kippenberg, Erik Norberg, Luke Theogarajan, Kerry Vahala, Nathan R. Newbury, Kartik Srinivasan, John E. Bowers, Scott A. Diddams & Scott B. Papp

https://www.nature.com/articles/s41586-018-0065-7 25 April 2018

A FULLY SELF-REFERENCED FREQUENCY COMB CONSUMING 5 WATTS OF ELECTRICAL POWER

We present a hybrid fiber/waveguide design for a 100-MHz frequency comb that is fully self-referenced and temperature controlled with less than 5 W of electrical power. Self-referencing is achieved by supercontinuum generation in a silicon nitride waveguide, which requires much lower pulse energies (~200 pJ) than with highly nonlinear fiber. These low-energy pulses are achieved with an erbium fiber oscillator/amplifier pumped by two 250-mW passively-cooled pump diodes that consume less than 5 W of electrical power. The temperature tuning of the oscillator, necessary to stabilize the repetition rate in the presence of environmental temperature changes, is achieved by resistive heating of a section of gold-palladium-coated fiber within the laser cavity. By heating only the small thermal mass of the fiber, the repetition rate is tuned over 4.2 kHz (corresponding to an effective temperature change of 4.2 °C) with a fast time constant of 0.5 s, at a low power consumption of 0.077 W/°C, compared to 2.5 W/°C in the conventional 200-MHz comb design.

Paritosh Manurkar, Edgar F. Perez, Daniel D. Hickstein, David R. Carlson, Jeff Chiles, Daron A. Westly, Esther Baumann, Scott A. Diddams, Nathan R. Newbury, Kartik Srinivasan, Scott B. Papp, and Ian Coddington

https://arxiv.org/pdf/1802.04119.pdf 7 Feb 2018

AN ULTRAFAST ELECTRO-OPTIC LIGHT SOURCE WITH SUB-CYCLE PRECISION

Controlling femtosecond optical pulses with temporal precision better than one cycle of the carrier field has a profound impact on measuring and manipulating interactions between light and matter. We explore pulses that are carved from a continuous-wave laser via electro-optic modulation and realize the regime of sub-cycle optical control without a mode-locked resonator. Our ultrafast source, with a repetition rate of 10 GHz, is derived from an optical-cavity-stabilized laser and a microwave-cavity-stabilized electronic oscillator. Sub-cycle timing jitter of the pulse train is achieved by coherently linking the laser and oscillator through carrier-envelope phase stabilization enabled by a photonic-chip supercontinuum that spans up to 1.9 octaves across the near infrared. Moreover, the techniques we report are relevant for other ultrafast lasers with repetition rates up to 30 GHz and may allow stable few-cycle pulses to be produced by a wider range of sources.

David R. Carlson, Daniel D. Hickstein, Wei Zhang, Andrew J. Metcalf, Franklyn Quinlan, Scott A. Diddams, and Scott B. Papp

https://arxiv.org/pdf/1711.08429.pdf 11 Nov 2017

QUASI-PHASE-MATCHED SUPERCONTINUUM-GENERATION IN PHOTONIC WAVEGUIDES

Supercontinuum generation in integrated photonic waveguides is a versatile source of broadband light, and the generated spectrum is largely determined by the phase-matching conditions. Here we show that quasi-phase-matching via periodic modulations of the waveguide structure provides a useful mechanism to control the evolution of ultrafast pulses and the supercontinuum spectrum. We experimentally demonstrate quasi-phase-matched supercontinuum to the TE20 and TE00 waveguide modes, which enhances the intensity of the SCG in specific spectral regions by as much as 20 dB. We utilize higher-order quasi-phase-matching (up to the 16th order) to enhance the intensity in numerous locations across the spectrum. Quasi-phase-matching adds a unique dimension to the design-space for SCG waveguides, allowing the spectrum to be engineered for specific applications.

Daniel D. Hickstein, Grace C. Kerber, David R. Carlson, Lin Chang, Daron Westly, Kartik Srinivasan, Abijith Kowligy, John E. Bowers, Scott A. Diddams and Scott B. Papp

arXiv:1710.03821v1 `{`physics.optics`}` 10 Oct 2017

OPTICAL-FREQUENCY MEASUREMENTS WITH A KERR-MICROCOMB AND PHOTONIC-CHIP SUPERCONTINUUM

Dissipative solitons formed in Kerr microresonators may enable chip-scale frequency combs for precision optical metrology. Here 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. This is achieved through a simple and reliable approach to deterministically generate, and subsequently frequency stabilize, soliton pulse trains in a silica-disk resonator. 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. We demonstrate the stabilized comb by performing a microcomb-mediated comparison of two ultrastable optical-reference cavities.

Erin S. Lamb, David R. Carlson, Daniel D. Hickstein, Jordan R. Stone, Scott A. Diddams and Scott B. Papp

arXiv:1710.02872v1 `{`physics.optics`}` 8 Oct 2017

AN INTEGRATED-PHOTONICS OPTICAL-FREQUENCY SYNTHESIZER

Integrated-photonics microchips now enable a range of advanced functionalities for high-coherence applications such as data transmission, highly optimized physical sensors, and harnessing quantum states, but with cost, efficiency, and portability much beyond tabletop experiments. Through high-volume semiconductor processing built around advanced materials there exists an opportunity for integrated devices to impact applications cutting across disciplines of basic science and technology. Here we show how to synthesize the absolute frequency of a lightwave signal, using integrated photonics to implement lasers, system interconnects, and nonlinear frequency comb generation. The laser frequency output of our synthesizer is programmed by a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and traceability to the SI second. This is accomplished with a heterogeneously integrated III/V-Si tunable laser, which is guided by dual dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through out-of-loop measurements of the phase-coherent, microwave-to-optical link, we verify that the fractional-frequency instability of the integrated photonics synthesizer matches the 7.01013 reference-clock instability for a 1 second acquisition, and constrain any synthesis error to 7.71015 while stepping the synthesizer across the telecommunication C band. Any application of an optical frequency source would be enabled by the precision optical synthesis presented here. Building on the ubiquitous capability in the microwave domain, our results demonstrate a first path to synthesis with integrated photonics, leveraging low-cost, low-power, and compact features that will be critical for its widespread use.

Daryl T. Spencer, Tara Drake, Travis C. Briles, Jordan Stone, Laura C. Sinclair, Connor Fredrick, Qing Li, Daron Westly, B. Robert Ilic, Aaron Bluestone, Nicolas Volet, Tin Komljenovic, Lin Chang, Seung Hoon Lee, Dong Yoon Oh, Myoung-Gyun Suh, Ki Youl Yang, Martin H. P. Pfeiffer, Tobias J.Kippenberg, Erik Norberg, Luke Theogarajan, Kerry Vahala, Nathan R. Newbury, Kartik Srinivasan, John E. Bowers, Scott A. Diddams, Scott B. Papp

Spencer2017_An Integrated-Photonics Optical-Frequency Synthesizer

PHOTONIC CHIP-BASED OPTICAL FREQUENCY COMB USING SOLITON CHERENKOV RADIATION

Optical solitons are propagating pulses of light that retain their shape because nonlinearity and dispersion balance each other. In the presence of higher-order dispersion, optical solitons can emit dispersive waves via the process of soliton Cherenkov radiation. This process underlies supercontinuum generation and is of critical importance in frequency metrology. Using a continuous wave–pumped, dispersion-engineered, integrated silicon nitride microresonator, we generated continuously circulating temporal dissipative Kerr solitons. The presence of higher-order dispersion led to the emission of red-shifted soliton Cherenkov radiation. The output corresponds to a fully coherent optical frequency comb that spans two-thirds of an octave and whose phase we were able to stabilize to the sub-Hertz level. By preserving coherence over a broad spectral bandwidth, our device offers the opportunity to develop compact on-chip frequency combs for frequency metrology or spectroscopy.

V.Brasch, M. Geiselmann, T. Herr, G. Lihachev, M. H. P. Pfeiffer, M. L. Gorodetsky, T. J. Kippenberg

Science, DOI: 10.1126/science.aad4811

HETEROGENEOUS INTEGRATION OF LITHIUM NIOBATE AND SILICON NITRIDE WAVEGUIDES FOR WAFER-SCALE PHOTONIC INTEGRATED CIRCUITS ON SILICON

An ideal photonic integrated circuit for nonlinear photonic applications requires high optical nonlinearities and low loss. This work demonstrates a heterogeneous platform by bonding lithium niobate (LN) thin films onto a silicon nitride (Si3N4Si3N4) waveguide layer on silicon. It not only provides large second- and third-order nonlinear coefficients, but also shows low propagation loss in both the Si3N4Si3N4 and the LNSi3N4LN-Si3N4 waveguides. The tapers enable low-loss-mode transitions between these two waveguides. This platform is essential for various on-chip applications, e.g., modulators, frequency conversions, and quantum communications.

Lin Chang, Martin H.P. Pfeiffer, Nicolas Volet, Michael Zervas, Jon D. Peters, Costanza L. Manganelli, Eric J. Stanton, Yifei Li, Tobias J. Kippenberg, and John E. Bowers

Vol. 42, No. 4 / February 15 2017 / Optics Letters 803

RADIATION HARDNESS OF HIGH-Q SILICON NITRIDE MICRORESONATORS FOR SPACE COMPATIBLE INTEGRATED OPTICS

Integrated optics has distinct advantages for applications in space because it integrates many elements onto a monolithic, robust chip. As the development of different building blocks for integrated optics advances, it is of interest to answer the important question of their resistance with respect to ionizing radiation. Here we investigate effects of proton radiation on high-Q (𝒪(106)) silicon nitride microresonators formed by a waveguide ring. We show that the irradiation with high-energy protons has no lasting effect on the linear optical losses of the microresonators.

Victor Brasch, Qun-Feng Chen, Stephan Schiller and Tobias J. Kippenberg,

Brasch2014

LOW-LOSS INTEGRATED PHOTONICS