GaSb-Si3N4 hybrid lasers with precise wavelength control and narrow spectral linewidth based on low-kappa Bragg gratings

Single-mode semiconductor laser operating near the 2 μm wavelength is of great interest for trace-gas detection, remote sensing, and infrared spectroscopy. Here, we present the 2 μm-wavelength-range laser sources with high output power, precise wavelength control, and narrow spectral linewidth enabled by hybrid integration of a GaSb-based gain chip with silicon nitride Bragg gratings. Low-kappa gratings are used as the laser feedback component to accurately select the lasing wavelength and increase the photon lifetime to achieve narrow-linewidth laser emission. The hybrid laser outputs 33.7 mW optical power with a side mode suppression ratio better than 40 dB near the 2 μm wavelength at room temperature. More than 20 lasers with an excellent wavelength spacing of 2.68 nm is demonstrated. The wavelength deviation is less than ±0.1 nm for all lasers. The intrinsic linewidth of the hybrid integrated external cavity laser with a 4.35 mm long feedback grating is measured to be ∼8.8 kHz using the phase noise demodulation method.