Wavelength tunable laser of small size

DETAILED DESCRIPTION An object of this invention is to provide a wavelength tunable laser device easy to be controlled and excellent in a wavelength selectivity.
Another object of this invention is to provide a wavelength tunable laser device easy to be controlled and capable of a high optical output.
According to one aspect of the present invention, there is provided a wavelength tunable laser device comprising: a pair of reflection mirrors; a semiconductor device disposed between the pair of reflection mirrors, the semiconductor device integrating a region for providing an optical gain, a region having a wavelength tunable filter function and a phase control region; and an optical filter disposed between the semiconductor device and one of the pair of reflection mirrors, the optical filter having periodical transmission wavelengths.
The semiconductor device having the gain region, wavelength tunable region and phase control region can be controlled easily by three electrodes.
A combination of the optical filter having the periodical sharp transmission wavelength characteristics and the semiconductor device can realize oscillation at a single wavelength.
A wavelength tunable laser device can be provided which has a high output, a broad tunable wavelength range and an easy control.