Patent ID: 8467427

Claim:
A light emitting and receiving device comprising: a semiconductor layer including: a first cladding layer; an active layer that is formed on an upper side of the first cladding layer; and a second cladding layer that is formed on an upper side of the active layer, a separation groove that electrically separates the semiconductor layer into a light emitting area and a light receiving area; a gain region that is formed in at least a part of the active layer that is located in the light emitting area, and the gain region is a continuous region extending from a first end surface disposed on a first side surface of the active layer that is located in the light emitting area to a second end surface disposed on the first side surface; a reflection surface that is formed at the gain region and that reflects light generated in the gain region between the first end surface and the second end surface; a mirror portion that is arranged on the reflection surface; a first electrode that is electrically connected to the first cladding layer located in the light emitting area; a second electrode that is electrically connected to the second cladding layer located in the light emitting area; a third electrode that is electrically connected to the first cladding layer located in the light receiving area; a fourth electrode that is electrically connected to the second cladding layer located in the light receiving area; and a second side surface that is located at an end of the light receiving area, that faces away from the separation groove, and that is opposite to the first side surface, wherein each of a first portion of the gain region that extends from the first end surface and a second portion of the gain region that extends from the second end surface is disposed in a direction tilted with respect to a perpendicular line of the first side surface in the plan view, a part of light generated in the first portion of the gain region is reflected by the reflection surface so as to be emitted from the second end surface, a part of light generated in the second portion of the gain region is reflected by the reflection surface so as to be emitted from the first end surface, a part of the light generated in the gain region transmits through the mirror portion arranged on the reflection surface, the light transmitting through the mirror portion is received in the light receiving area of the semiconductor layer, and a length that corresponds to a distance between the separation groove and the second side surface is (2m c +1)λ/4n c , where m c is an integer equal to or greater than zero, λ is a wavelength of the light generated in the gain region, and n c is an effective refractive index of a vertical section of the light receiving area.