Integrated small-sized semiconductor ring laser with novel retro-reflector cavity

We have successfully designed and fabricated 1.55-mu m semiconductor ring lasers with novel parabolic mirror retro-reflector cavities. The parabolic mirror is designed by means of ray-tracing and finite-difference time-domain to optimize its shape and position. The fabricated devices, with a range of sizes down to an equivalent circular ring radius of 16 mu m, operate in continuous-wave mode at room temperature. Threshold current of 22 mA and output power up to 140 mu W have been achieved for the smallest device. These devices are suitable for high-speed all-optical signal processing and digital photonic functions.