Sub-kHz linewidth, hybrid III-V/silicon wavelength-tunable laser diode operating at the application-rich 1647-1690 nm

The wavelength region about of 1650 nm enables pervasive applications. Some instances include methane spectroscopy, free-space/fiber communications, LIDAR, gas sensing (i.e. C2H2, C2H4, C3H8), surgery and medical diagnostics. In this work, through the hybrid integration between an III-V optical amplifier and an extended, low-loss wavelength tunable silicon Vernier cavity, we report for the first time, a III-V/silicon hybrid wavelength-tunable laser covering the application-rich wavelength region of 1647-1690 nm. Room-temperature continuous wave operation is achieved with an output power of up to 31.1 mW, corresponding to a maximum side-mode suppression ratio of 46.01 dB. The laser is ultra-coherent, with an estimated linewidth of 0.7 kHz, characterized by integrating a 35 km-long recirculating fiber loop into the delayed self-heterodyne interferometer setup. The laser linewidth is amongst the lowest in hybrid/heterogeneous III-V/silicon lasers.