Investigation of the Long-Term Stability of a Local Oscillator Generator Based on InP-Si₃N₄ Laser Source for Satellite Payloads

Abstract

We report an experimental characterization of the long-term stability of a local oscillator (LO) signal generation module for satellite communications based on the optical heterodyning of two InP/Si3N4 hybrid integrated lasers. Specifically, we analyze simultaneously the wavelength drift of both lasers in the optical domain and the electrical drift of the generated radiofrequency (RF) beat between the lasers. We identify the main factors that contribute to the overall drift such as the electrical noise coming from the supply sources, the thermal noise coming from the temperature control unit, and the thermal crosstalk between lasers. This investigation compares the stability of an RF signal generated by two approaches. Using two integrated lasers and using a combination of one integrated laser with one external laser. This work also analyzes the difference when lasers are mounted over a standard breadboard with a thermallycontrolled. The results show that the best approach is to use both integrated lasers on the same chip. We report a 25 GHz RF signal with long-term stability of 30 MHz measured over 10 hours under free-running operation mode. Moreover, we experimentally demonstrate that integrated lasers can be stabilized by using injection locking. We experimentally demonstrate the optical injection locking of two hybrid InP/Si3N4 lasers when the leader laser and the follower laser are both hybrid integrated lasers of same system on chip. When the laser is locked, we report a locking range of 1.86 GHz.