An optical receptacle configured to optically couple a vertical-cavity surface-emitting laser and an end surface of an optical transmission member in a state where the optical receptacle is disposed between the optical transmission member and the photoelectric conversion device, the photoelectric conversion device including the vertical-cavity surface-emitting laser and a detection device configured to monitor light emitted from the vertical-cavity surface-emitting laser, the optical receptacle comprising:
- a first optical surface configured to allow incidence of light emitted from the vertical-cavity surface-emitting laser;
- a first reflection part configured to reflect, as monitor light travelling toward the detection device, a part of light entered from the first optical surface;
- a light separation part configured to separate another part of the light entered from the first optical surface into monitor light travelling toward the detection device and signal light travelling toward the end surface of the optical transmission member;
- a second optical surface configured to emit, toward the end surface of the optical transmission member, the signal light separated at the light separation part;
- and
- a third optical surface configured to emit, toward the detection device, the monitor light reflected by the first reflection part and the monitor light separated at the light separation part,
- wherein the light separation part includes:
- two second reflection parts tilted to an optical axis of the light entered from the first optical surface, the two second reflection parts being configured to reflect a part of light incident on the light separation part toward the third optical surface as the monitor light travelling toward the detection device, and
- a transmission part disposed at least between the two second reflection parts, and configured to transmit, as the signal light, another part of the light incident on the light separation part;
- and
- wherein the two second reflection parts are disposed within a light flux of the light entered from the first optical surface to satisfy a following installation method of the two second reflection parts,
- the installation method of the two second reflection parts of the two second reflection parts comprising:
- (1) determining a first curve, the first curve representing a relationship between an angle to a normal passing through a center of a light-emitting surface of the vertical-cavity surface-emitting laser in a cross-section that includes the normal and is parallel to an arrangement direction of the two second reflection parts, and a light intensity of light emitted from the light-emitting surface when a maximum available current is applied to the vertical-cavity surface-emitting laser, wherein a direction along the normal is set to 0° in the cross-section;
- (2) determining a first maximum value and a second maximum value in the first curve, the first maximum value being a maximum value of a light intensity in a minus region of the angle, the second maximum value being a maximum value of a light intensity in a plus region of the angle, wherein in the first curve, the angle to the normal on one side with respect to the normal in the cross-section is set as minus, and the angle to the normal on another side with respect to the normal in the cross-section is set as plus;
- (3) determining a second curve, the second curve representing a relationship between the angle to the normal in the cross-section and the light intensity of the light emitted from the vertical-cavity surface-emitting laser when an available minimum current is applied to the vertical-cavity surface-emitting laser, wherein the direction along the normal is set to 0°;
- (4) determining a first minimum difference angle, the first minimum difference angle being an angle corresponding to a state where a difference between a light intensity in the first curve and a light intensity in the second curve is smallest in a range from an angle of 0° to an angle corresponding to the first maximum value;
- (5) determining a second minimum difference angle, the second minimum difference angle being an angle corresponding to a state where a difference between the light intensity in first curve and the light intensity in second curve is smallest in a range from the angle of 0° to an angle corresponding to the second maximum value;
- and
- (6) disposing the two second reflection parts at arrival positions of light emitted at the first minimum difference angle and light emitted at the second minimum difference angle.