Patent ID: 7071524

Claim:
A semiconductor light receiving device comprising: a substrate; a lower cladding layer which has a predetermined refractive index, is laminated on an upper portion of the substrate, and is constituted of at least one layer; a light absorption layer laminated on an upper portion of the lower cladding layer; an upper cladding layer which has a refractive index smaller than a refractive index of said at least one layer constituting the lower cladding layer, is laminated above the light absorption layer, and is constituted of at Least one layer; and a light incident end surface which is provided at both the substrate and the lower cladding layer, and, when a light is made incident at a predetermined angle, enables the light to be absorbed in the light absorption layer and to be output as a current, wherein the light incident on both the substrate and the lower cladding layer providing the light incident end surface senses a refractive index of the lower cladding layer so that an equivalent refractive index of the light becomes larger, and the equivalent refractive index of the light becomes larger than a refractive index of said at least one layer constituting the upper cladding layer having a refractive index smaller than a refractive index of said at least one layer constituting the lower cladding layer, and the predetermined angle is an angle enabling a light incident on the light absorption layer to be reflected at a lower surface of at least one layer constituting the upper cladding layer, so that the light can be repeatedly propagated through the light absorption layer.