Patent ID: 7446293

Claim:
An electro-optical element, comprising: a light-emitting element part including a mirror; and a light-receiving element part formed on the mirror; wherein: the electro-optical element is one of an npnp or a pnpn construction; and an optical thickness d of the light-receiving element part satisfies the following condition (1): d=mλ/ 2 (1) where: λ is a design wavelength of the light-emitting element part, m is a natural number greater than or equal to one, and an optical member provided at least on an optical surface of the light-receiving element part, wherein: a cross-sectional surface of the optical member cut by a plane parallel to the optical surface being at least one of a circle and an oval; at least an upper part of the light-emitting element part has a columnar like shape; and a longest diameter of the cross-sectional surface of the optical member being larger than a longest diameter of an upper surface of the light-receiving element part.