Optical semiconductor device and semiconductor laser device

An optical semiconductor device comprising:

• an active layer including a plurality of quantum dot layers,
• wherein the plurality of quantum dot layers includes at least one quantum dot layer doped with a p-type impurity, and
• wherein the plurality of quantum dot layers includes at least two quantum dot layers having different emission wavelengths and different p-type impurity concentrations from each other,
• wherein the at least two quantum dot layers having the different emission wavelengths and different p-type impurity concentrations from each other includes:
• at least two first quantum dot layers having a first emission wavelength shorter than a predetermined emission wavelength, doped with the p-type impurity, and disposed adjacent to each other, the predetermined emission wavelength corresponding to an operating wavelength of the active layer at a predetermined temperature;
• and
• at least two second quantum dot layers having a second emission wavelength longer than the predetermined emission wavelength, and undoped,
• wherein
• the active layer further includes a p-type impurity layer disposed between the at least two first quantum dot layers adjacent to each other, and
• the at least two second quantum dot layers are disposed adjacent to each other without interposing a p-type impurity layer therebetween.