Miniature narrow-linewidth 1 μm laser

A self-injection locking scheme has the potential to narrow the linewidth of lasers in a compact setup. Here, we report a narrow linewidth laser source near 1 μm by the self-injection locking scheme using a Fabry-Pérot (FP) hollow resonator with a high-quality factor (Q > 10⁸). The measured fundamental linewidth of the laser is 41 Hz, and a coarse tuning range over 5.5 nm is achieved by changing the driving current of the laser source. Meanwhile, a fine-tuning range of 373 MHz is achieved without mode hops by changing the voltage applied to the PZT on the resonator. More importantly, benefiting from the low thermal refractive noise and low thermal expansion of the FP hollow resonator, the beat-note linewidth and the frequency Allan deviation are measured to be 510.3 Hz in and 10⁻¹¹ (1 s of averaging time), respectively, by using a fully stabilized frequency comb as a reference. Such a high-performance laser is fully integrated with a palm-sized package (52.3 ml) for field-deployable applications.