Semiconductor laser device.

摘要

A wavelength-tunable semiconductor laser device presenting a large wavelength-tunable range or a very-high-speed modulating semiconductor laser device having a distributed feedback structure including a diffraction grating (112) as in the case of a DBR laser or a DFB laser incorporates therein a plurality of active layers (141, 105) differing from one another in constituent elements or composition ratio or thickness for reducing spectral line widths, while improving single-mode spectral oscillation characteristics.