Semiconductor laser device

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.