| abstract |
(57) [Abstract] [PROBLEMS] To provide a wavelength tunable semiconductor laser device having a wide wavelength tunability and not having a wide spectral linewidth when the wavelength is tuned. In a wavelength tunable DFB semiconductor laser device, a plurality of active regions having different carrier density-gain characteristics are provided in the same resonator by changing the quantum well structure (for example, the number of wells) of the active region along the resonator direction. 21, 22a, 22b are provided, and a plurality of electrodes 18 1 , 18 2 , 18 3 are provided corresponding to these active regions 21, 22a, 22b. |