Optical semiconductor device and manufacturing method therefor

1. A manufacturing method for an optical semiconductor device, comprising:

disposing a semiconductor element that has a polarization dependent gain or a polarization dependent loss between optical waveguide modes differing in a direction of polarization;

positioning a lens at one end face side of the semiconductor element based on an optical coupling loss between the lens and the semiconductor element;

repositioning the lens based on the polarization dependent gain or the polarization dependent loss of the semiconductor element,

wherein a spot size at a beam waist position of the lens is smaller than a spot size in any of the optical waveguide modes in the semiconductor element, and the repositioning of the lens includes:

inputting light in the optical waveguide modes differing in the direction of polarization to the semiconductor element;

detecting light in the optical waveguide modes differing in the direction of polarization output from the semiconductor element through the lens; and

carrying out positional adjustment by displacing the lens in an optical axis direction in such a manner that an amplitude of a temporal waveform of the power of the light detected through the lens approximately equals zero,

wherein the light in the optical waveguide modes differing in the direction of polarization is polarization-scrambled light.

2. The manufacturing method for an optical semiconductor device according to claim 1 , wherein the lens includes a first lens and a second lens, and the positioning of the lens comprises:

positioning the first lens and the second lens at the one end face side of the semiconductor element front to back in such a manner that the first lens is closer to the semiconductor element than the second lens; and

fixing the second lens at a position where light passing through the first lens and the second lens forms collimated light.

3. The manufacturing method for an optical semiconductor device according to claim 1 , wherein the positioning the lens further comprises:

positioning another lens at the other end face side of the semiconductor element.

4. The manufacturing method for an optical semiconductor device according to claim 3 , wherein the another lens includes a third lens and a fourth lens, and the positioning of the another lens comprises:

disposing the third lens and the fourth lens front to back in such a manner that the third lens is closer to the semiconductor element than the fourth lens; and

fixing the fourth lens at a position where light passing through the third lens and the fourth lens forms collimated light.

5. The manufacturing method for an optical semiconductor device according to claim 3 , wherein the repositioning of the lens comprises:

inputting light in the optical waveguide modes differing in the direction of polarization to the semiconductor element through the another lens.

6. The manufacturing method for an optical semiconductor device according to claim 3 , wherein the repositioning of the lens further comprises:

detecting light in the optical waveguide modes differing in the direction of polarization output from the semiconductor element through the another lens; and

repositioning the another lens based on detected light.

7. The manufacturing method for an optical semiconductor device according to claim 6 , wherein the repositioning of the lens comprises:

inputting light in the optical waveguide modes differing in the direction of polarization to the semiconductor element through the lens.

8. The manufacturing method for an optical semiconductor device according to claim 7 , wherein the repositioning of the lens comprises:

repositioning the lens and the another lens at positions where the polarization dependent gain or the polarization dependent loss of the semiconductor element is reduced.

9. The manufacturing method for an optical semiconductor device according to claim 8 , wherein the light in the optical waveguide modes differing in the direction of polarization is polarization-scrambled light, and the repositioning of the lens comprises:

carrying out positional adjustment by displacing the lens in an optical axis direction in such a manner that the amplitude of a temporal waveform of the power of the light detected through the lens approximately equals a specified value and carrying out positional adjustment by displacing the another lens in the optical axis direction in such a manner that the amplitude of a temporal waveform of the power of the light detected through the another lens approximately equals 0.

10. The manufacturing method for an optical semiconductor device according to claim 1 , wherein the lens includes a lens fiber processed to have a lens-like tip end.

11. The manufacturing method for an optical semiconductor device according to claim 3 , wherein the another lens includes a lens fiber processed to have a lens-like tip end.