Semiconductor laser device

1 . A semiconductor laser device in which a distributed feedback laser part and an electro-absorption modulator part are formed on the same semiconductor substrate, the semiconductor laser device comprising:

the laser part including a first diffraction grating formed to extend in a direction of an optical axis of laser light emitted from the laser part;

the modulator part partially including a second diffraction grating formed to extend in the direction of the optical axis of the laser, wherein in a view perpendicular to the optical axis, the second diffraction grating entirely overlaps the modulator part; and

an anode electrode of the modulator part formed on a front side of the semiconductor substrate and terminating at an emission end face of the modulator part, wherein:

a non-diffraction grating region in which a diffraction grating is not formed is interposed between the second diffraction grating of the modulator part and an emission end face of the laser part from which the laser light is emitted to the modulator part;

the laser light is emitted from the emission end face of the modulator part;

the laser part includes an anode electrode, and an insulation layer is formed directly between the anode electrode of the laser part and the anode electrode of the modulator part,

wherein the insulation layer is also positioned between the anode electrode of the modulator part and the second diffraction grating.

2 . The semiconductor laser device according to claim 1 , wherein

the first diffraction grating includes a plurality of first protrusions extending in a direction perpendicular to the semiconductor substrate, and a plurality of first recesses being recessed toward the semiconductor substrate from faces of the first protrusions on a side opposite to the semiconductor substrate;

the second diffraction grating includes a plurality of second protrusions extending in the direction perpendicular to the semiconductor substrate, and a plurality of second recesses being recessed toward the semiconductor substrate from faces of the second protrusions on a side opposite to the semiconductor substrate; and

the second recesses of the second diffraction grating have the same depth in the direction perpendicular to the semiconductor substrate as that of the first recesses of the first diffraction grating.

3 . The semiconductor laser device according to claim 2 , wherein the second diffraction grating is non-uniform in thickness in the second recesses in the direction perpendicular to the semiconductor substrate.

4 . The semiconductor laser device according to claim 2 , wherein the second diffraction grating is formed of the same diffraction grating material layer as the first diffraction grating.

5 . The semiconductor laser device according to claim 1 , wherein

the first diffraction grating includes a plurality of first protrusions extending in a direction perpendicular to the semiconductor substrate, and a plurality of first recesses being recessed toward the semiconductor substrate from faces of the first protrusions on a side opposite to the semiconductor substrate;

the second diffraction grating includes a plurality of second protrusions extending in the direction perpendicular to the semiconductor substrate, and a plurality of second recesses being recessed toward the semiconductor substrate from faces of the second protrusions on a side opposite to the semiconductor substrate; and

the second diffraction grating is non-uniform in depth in the second recesses in the direction perpendicular to the semiconductor substrate.

6 . The semiconductor laser device according to claim 5 , wherein the second diffraction grating has a uniform interval in the direction of the optical axis of the laser light in each second protrusion and each second recess that are adjacent in a pair.

7 . The semiconductor laser device according to claim 5 , wherein the second diffraction grating is non-uniform in thickness in the second recesses in the direction perpendicular to the semiconductor substrate.

8 . The semiconductor laser device according to claim 1 , wherein the second diffraction grating is formed of the same diffraction grating material layer as the first diffraction grating.

9 . The semiconductor laser device according to claim 1 , wherein the non-diffraction grating region is provided on a side to the laser part in the modulator part.

10 . The semiconductor laser device according to claim 1 , further comprising:

a cathode electrode formed on a rear surface of the semiconductor substrate;

an anode electrode of the laser part formed on a front side of the semiconductor substrate; and

a separation part in which the anode electrode of the modulator part is separated from the anode electrode of the laser part, the separation part being provided between the modulator part and the emission end face of the laser part.

11 . The semiconductor laser device according to claim 1 , further comprising:

the laser part including a first mesa stripe that is a mesa formed to extend in the direction of the optical axis of the laser light and includes an active layer and the first diffraction grating;

the modulator part including a second mesa stripe that is a mesa formed to extend in the direction of the optical axis of the laser light and includes an absorption layer and the second diffraction grating, and

the non-diffraction grating region including a third mesa stripe that is a mesa formed to extend in the direction of the optical axis of the laser light and includes an absorption layer connected to the absorption layer of the modulator part and the active layer of the laser part, the non-diffraction grating region being provided between an end of the modulator part on the side to the laser part and the emission end face of the laser part from which the laser light is emitted to the modulator part; wherein

the first mesa stripe, the second mesa stripe, and the third mesa stripe are continuous.

12 . The semiconductor laser device according to claim 1 , wherein in the view perpendicular to the optical axis, an entirety of the second diffraction grating overlaps the anode electrode.

13 . A semiconductor laser device in which a distributed feedback laser part and an electro-absorption modulator part are formed on the same semiconductor substrate, the semiconductor laser device comprising:

the laser part including a first diffraction grating formed to extend in a direction of an optical axis of laser light emitted from the laser part; and

the modulator part at least partially including a second diffraction grating formed to extend in the direction of the optical axis of the laser and the modulator part further comprising an anode electrode of the modulator part formed on a front side of the semiconductor substrate and terminating at an emission end face of the modulator part, wherein

a non-diffraction grating region in which a diffraction grating is not formed is interposed between the second diffraction grating of the modulator part and an emission end face of the laser part from which the laser light is emitted to the modulator part;

wherein the first diffraction grating includes a plurality of first protrusions extending in a direction perpendicular to the semiconductor substrate, and a plurality of first recesses being recessed toward the semiconductor substrate from faces of the first protrusions on a side opposite to the semiconductor substrate;

the second diffraction grating includes a plurality of second protrusions extending in the direction perpendicular to the semiconductor substrate, and a plurality of second recesses being recessed toward the semiconductor substrate from faces of the second protrusions on a side opposite to the semiconductor substrate; and

the second recesses of the second diffraction grating have the same depth in the direction perpendicular to the semiconductor substrate as that of the first recesses of the first diffraction grating; and

wherein:

the second diffraction grating has a uniform interval in the direction of the optical axis of the laser light in each second protrusion and each second recess that are adjacent in a pair,

the laser light is received by the modulator part and emitted from the emission end face of the modulator part,

in a view perpendicular to the optical axis, the second diffraction grating entirely overlaps the modulator part;

the laser part includes an anode electrode, and an insulation layer is formed directly between the anode electrode of the laser part and the anode electrode of the modulator part,

wherein the insulation layer is also positioned between the anode electrode of the modulator part and the second diffraction grating.

14 . The semiconductor laser device according to claim 13 , wherein the second diffraction grating is non-uniform in thickness in the second recesses in the direction perpendicular to the semiconductor substrate.

15 . The semiconductor laser device according to claim 13 , wherein the second diffraction grating is formed of the same diffraction grating material layer as the first diffraction grating.

16 . The semiconductor laser device according to claim 13 , wherein in the view perpendicular to the optical axis, an entirety of the second diffraction grating overlaps the anode electrode.