Highly reliable InP-based PIN-photodiode array monolithically integrated with 90° hybrid MMI using butt-joint regrowth

Highly reliable InP-based pin-photodiode arrays monolithically integrated with a 90° hybrid consisting of MMI using the butt-joint regrowth were demonstrated for 100 Gb/s coherent receivers. Responsivity imbalance of all channels was less than ±0.5 dB owing to the phase adjustment of waveguides between MMIs. The wide 3-dB bandwidth of 26 GHz was obtained at a low bias voltage of −1.6 V. The dark current (bias: −3.0 V) was as low as 0.2 nA by optimizing the thickness of InP passivation, and the stable dark current was achieved in the accelerated aging test (−5 V at 175 °C) over 2,000 h.