Phase-Shifted Distributed Feedback Lasers With Two-Layer Moiré Gratings

Abstract

Single-wavelength distributed feedback (DFB) lasers are widely used in high-speed access networks; however, the device yield is generally low due to threshold degeneracy resulting from uniform periodic gratings. In this work, we propose and experimentally demonstrate a two-layer moire grating structure to provide a quarter-wavelength phase shift in DFB lasers. The grating structure can be defined easily using low-cost laser interference lithography. In experiments, 200- $\mu \text{m}$ -long DFB lasers exhibit excellent single-wavelength operating behavior (SMSR >42 dB) in terms of Bragg wavelength and high-speed modulation capability ( $\text{f}_{\mathrm {3dB}} =22$ GHz). High device yield of 86% from 320 laser dies further validated the efficacy of the proposed DFB laser design as a promising alternative to existing phase-shifted DFB laser solutions.