High responsivity evanescently coupled waveguide photodiode using spot-size converter and distributed Bragg reflector at 1.55 μm wavelength

InGaAs/InP waveguide photodiode, one of the most crucial devices in optical modules, has proven to be beneficial for exponential data communication. However, improving responsivity with a high 3 dB bandwidth remains a challenge for various photodetector designs. In this letter, a multi-layers SiO2/SiNx distributed Bragg reflector and a spot-size converter are both employed and improve responsivity by 61%. An optimized optical matching layer and a spot-size converter combined with the reflector lead to a 0.66 A/W responsivity at 1550 nm wavelength. 3 dB bandwidth of the device can achieve 85 GHz with a 3μm × 10 μm active area. The responsivity improvement indicates a higher quantum efficiency and signal-to-noise ratio. It could be beneficial for high speed optical communication and other applications.