A novel demultiplexing photodetector with integrated vertical taper structure

A novel demultiplexing photodetector which consists of a filtering cavity and a taper absorption cavity is proposed. The filtering cavity is formed by five coupled (Fabry–Pérot) F–P cavities, which can realize flat-top and steep-edge spectral response. The top mirror of the absorption cavity is designed to be a vertical taper structure, which can increase the times of light reflection. Then the quantum efficiency is improved. Through the theoretical analysis and simulation, the peak quantum efficiency of the photodetector is improved. The photodetector is fabricated by bonding a Si-based multi-cavity F–P filter with an InP-based vertical taper structure. An integrated device with a peak quantum efficiency of 58.42% around 1550 nm is obtained. In addition, this photodetector has good performance in the flat-top and steep-edge spectral response, the spectral linewidth is less than 0.65 nm. The passband flatness is less than 0.55 dB. The −0.5 dB band is 0.52 nm, and the 25 dB band is 0.95 nm.