A novel integrated demultiplexing photodetector which consists of a filter cavity and an arc absorbing
cavity is proposed in this paper. The top mirror of absorbing cavity is designed to be curved, which can
increase the times of light reflection. The maximum quantum efficiency of TE lightwave can reach
81.84%, while maximum of TM is 65.62%. An obvious near-to-zero domain of reflectivity of TM
lightwave leads to its low quantum efficiency. The impact of incident angle on quantum efficiency is
demonstrated by comparing two series of incident angles in two devices which have high and low
quantum efficiency respectively. In addition, the spectral response linewidth of this novel
photodetector is less than 0.8 nm.