Tunable multi-wavelength generation of an integrated self-injection locking laser based on the Vernier effect

A narrow-linewidth laser based on self-injection locking has found widespread applications, including wavelength division multiplexing, sensing, and LiDAR detection. Although self-injection locking can support multi-wavelength operation, conventional implementations have typically been bulky and constrained by limited wavelength spacing. In this paper, we demonstrate an integrated multi-wavelength self-injection locking (MWSIL) laser capable of generating multiple narrow-linewidth outputs with tunable spacing. Multi-wavelength operation is achieved through the Vernier effect in the injection locking of a single distributed feedback laser (DFB) to a Si₃N₄-based micro-resonator (MRR). In the experimental demonstration, the wavelength spacing of the laser is tunable from 1.155 nm to 9.24 nm by adjusting the phase of the cavity. The intrinsic linewidths of the multi-wavelength laser are all below 1.6 kHz, with the optimal linewidth at 125 Hz, representing up to a 703-fold improvement compared to the free-running state. Additionally, the laser exhibits mode-hop-free frequency tuning over a range of 2.6 GHz. The MWSIL laser provides an effective on-chip solution for generating a tunable, multi-wavelength optical source with ultra-narrow linewidth.