Compact and temperature-insensitive wavelength detectors integrated with widely tunable external-cavity lasers

We propose and realize a compact and temperature-insensitive wavelength detector, integrated with a widely tunable external-cavity laser based on the standard silicon photonic platform. The fabricated wavelength detector is comprised of a hybrid Mach-Zehnder Interferometer (MZI) with silicon and silicon-nitride waveguides. The minimum temperature sensitivity of -0.28pm/K with the extinction ratio up to 28 dB is achieved, benefitting from the large difference of thermal-optic coefficients between silicon and silicon-nitride waveguides. Moreover, a widely tunable external-cavity laser is designed and fabricated, adopting the hybrid MZI wavelength detector as an on-chip wavelength locker. The wavelength tuning range from 1546.6 nm to 1647.2 nm is measured with the side-mode suppression ratio larger than 45 dB. The picometer-level wavelength monitoring accuracy is experimentally verified through the feedback of photocurrents from Ge/Si photodetectors, which validates the accuracy and robustness of the device.