Frequency noise performance improvement of mutually injection-locked semiconductor lasers

摘要

The frequency noise characteristic of lasers under mutual injection locking is investigated. Pronounced frequency noise suppression is demonstrated for two distributed feedback lasers mutually coupled through a fiber link with 60 ns delay, confirmed by both local oscillator heterodyne and delayed self-heterodyne methods. Locking can be secured for the weak-coupling regime and a locking map is derived. The frequency noise of the laser under mutual injection locking is found to improve with increasing coupling strength or injection current. The single-sided white frequency noise of the laser is estimated to be below 3 Hz(2) Hz(-1), corresponding to an intrinsic linewidth narrower than 9.4 Hz. (c) 2019 The Japan Society of Applied Physics