Ultra-low-noise laser at 1064  nm through self-injection locking to an asymmetric-mode-splitting microring resonator

Low-noise lasers in the 1-μm band play a crucial role in modern photonic systems, yet their chip-scale implementation remains at an early stage compared to lasers operating at the communication band, leaving significant untapped potential for exploration. Here, a low-noise hybrid integrated laser emitting at 1064 nm is demonstrated, through using a semiconductor laser self-injection locked to a Si 3 N 4 -based microring resonator (MRR). The MRR distinguishes itself by embedding a lossy defect to cause asymmetric mode splitting, achieving an enhanced loaded Q of 5.1×10 6 . The self-injection locked laser presents a fiber-coupled output power of 14.79 dBm and achieves an intrinsic linewidth of 26.8 Hz and a 1/ π -integral linewidth of 2.3 kHz, representing the narrowest intrinsic linewidth reported to date for integrated 1-μm lasers. The demonstrated laser opens up new opportunities in high-resolution spectroscopy measurement, green light generation, and quantum sensing.