A common platform decision
SiN and SOI are the two dominant CMOS-compatible platforms for passive photonic ICs. Key differences:
Propagation loss: LIGENTEC SiN achieves < 0.5 dB/m. SOI typically 2–3 dB/cm — roughly two orders of magnitude higher. For high-Q resonators, long delay lines, or cascaded passives, this difference is decisive.
Wavelength range: SiN is transparent from the visible (~400 nm) to mid-IR (>3 µm). SOI operates from ~1.1 µm — it cannot be used at visible wavelengths. For biophotonics, quantum emitters, or atomic transitions in the 600–900 nm range, SiN is the only viable mature CMOS-compatible option.
Nonlinear performance: SiN exhibits negligible two-photon absorption at telecom wavelengths — a key material advantage enabling efficient frequency comb generation, four-wave mixing, and supercontinuum generation. TPA in SOI limits effective nonlinear interaction length and generates free carriers that increase loss.
Power handling: SiN’s high damage threshold supports watt-level optical power in waveguides (up to 10 W tested for LIDAR). SOI’s free-carrier effects constrain usable power at high intensity.
Integration density and active functions: SOI’s higher index contrast enables tighter bends and smaller components, plus native Ge photodetection and plasma-dispersion electro-optic modulation. SiN’s standard platforms are passive at the waveguide core level; active functions are added via LIGENTEC LABS integration modules (TFLN, InGaAs).
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See also: SiN · AN800 · AN350 · Heterogeneous Integration · Propagation Loss · TFLN