Hybrid integrated narrow linewidth laser based on high-order SiO ₂ planar waveguide grating

We propose and demonstrate a hybrid integrated external cavity narrow linewidth laser, which consists of a reflective semiconductor optical amplifier chip and a high-order SiO₂-based planar waveguide grating (SPWG). The proposed laser has the characteristics of high power, narrow linewidth, and low relative intensity noise (RIN). At 300 mA pump current, the laser exhibits a single longitudinal mode with 55 mW output power, 614 Hz Lorentzian linewidth, and the RIN is -165 dBc/Hz @ 100 MHz to 250 MHz. This work realizes high-power, narrow-linewidth lasers via a simple high-order SPWG structure and a low-loss commercial SiO₂ platform. This approach resolves the traditional linewidth-power tradeoff, which can be used for mass production.