Patent ID: 7372124

Claim:
An optical demultiplexer for demultiplexing an incident light including multiplexed wavelengths, comprising: an optical means for demultiplexing the incident light into a plurality of lights, the incident light including N (N is an integer equal to or larger than 2) time-divisioned wavelengths; and a photodetector for receiving the plurality of lights demultiplexed by the optical means, and detecting a light intensity and a barycenter thereof for each of lights demultiplexed from the incident light, the photodetector including N light-receiving elements arrayed in one dimension, wherein each light-receiving element includes: a semiconductor layer of Ill-V group compound semiconductor, a first conductivity-type of resistor layer provided on a top surface of the semiconductor layer, a second conductivity-type, opposite to the first conductivity-type of substrate provided beneath a bottom surface of the semiconductor layer, the resistor layer and the substrate each being III-V semiconductor layers, and first and second electrodes provided on the resistor layer separated by a region of the resistor layer, wherein light incident on the region from one of the corresponding plurality of lights generates a first signal to the first electrode and a second signal to the second electrode, the first and second signals indicating a position of the light incident on the resistor layer within the region relative to the first and second electrodes, the incident light being incident on the resistor layer without first passing through any conductive layer.