WAVEGUIDE TYPE PHOTODETECTOR

摘要

A waveguide type light receiving element (10) comprises a photodetector section (14), a photo-attenuator section (18), and an electrical isolation section (20) having a light transmission property which electrically isolates the photodetector section from the photo-attenuator section for allowing light transmission. The photodetector section comprises n-type light guide layer (28) and i-type light absorption layer (30) formed on a substrate 22, and a pair of n- and p-type light confinement layers (26 and 32) which sandwich the light guide layer and the light absorption layer therebetween, thereby forming a double hetero-junction structure. The photo-attenuator section has a layer structure similar to the photodetector section except for a strained MQW layer disposed instead of the light absorption layer and has an absorption controlling electrode (16) and an electrode (40) disposed on the top and bottom, respectively, of the substrate. The light absorption layer and the waveguide of the photodetector section and the photo-attenuator section form a ridge structure to have a light confinement structure in a horizontal direction as well as a light confinement structure in a vertical direction. By applying a reverse bias voltage between the electrodes of the photo-attenuator section, the amount of absorption of the incident light by the photo-attenuator section can be controlled, thereby controlling the intensity of light propagated to the photodetector section.