Wavelength tunable semiconductor laser device

A wavelength tunable semiconductor laser device comprising:

• a semiconductor substrate of a first conductivity type;
• a semiconductor active layer located opposite the semiconductor substrate and producing light in response to current injected into the active layer, the light having a wavelength;
• a semiconductor tuning layer located opposite the semiconductor substrate and having a refractive index that varies in response to an electric field applied to the tuning layer, the tuning layer tuning the wavelength of the light produced by the laser in response to the refractive index controlled by the electric field applied to the tuning layer;
• a semiconductor spacer layer of a second conductivity type, opposite the first conductivity type, interposed between the active layer and the tuning layer;
• front and rear resonator facets located at opposite ends of the semiconductor active layer and of the semiconductor tuning layer and having different reflectivities from each other;
• a first electrode in electrical contact with the semiconductor substrate for applying an electric field to the semiconductor tuning layer;
• a second electrode in electrical contact with the tuning layer for injecting current into the semiconductor active layer, the second electrode being divided into a plurality of portions in a resonator length direction of the semiconductor laser;
• and
• a third electrode commonly used with the first and second electrodes, the third electrode being in electrical contact with the semiconductor spacer layer.

A wavelength tunable semiconductor laser device comprising:

• a semiconductor substrate of a first conductivity type;
• a semiconductor active layer located opposite the semiconductor substrate and producing light in response to current injected into the active layer, the light having a wavelength;
• a semiconductor tuning layer located opposite the semiconductor substrate and comprising a plurality of regions arranged in a resonator length direction of the laser, the regions providing respective different variations in refractive index and light absorption in response to an applied electric field, the tuning layer tuning the wavelength of the light produced by the laser in response to the refractive index controlled by the electric field applied to the tuning layer;
• a semiconductor spacer layer of a second conductivity type, opposite the first conductivity type, interposed between the active layer and the tuning layer;
• front and rear resonator facets located at opposite ends of the semiconductor active layer and of the semiconductor tuning layer and having different reflectivities from each other;
• a first electrode in electrical contact with the tuning layer for applying an electric field to the semiconductor tuning layer, the first electrode being divided into a plurality of portions in a resonator length direction of the semiconductor laser;
• a second electrode disposed on the semiconductor substrate for injecting current into the semiconductor active layer;
• and
• a third electrode common to the first and second electrodes, the third electrode being in electrical contact with the semiconductor spacer layer.

A wavelength tunable semiconductor laser device comprising:

• a semiconductor substrate;
• a semiconductor active layer located opposite the semiconductor substrate and producing light in response to current injected into the active layer, the light having a wavelength;
• a semiconductor tuning layer located opposite the semiconductor substrate and having a refractive index that varies in response to an electric field applied to the tuning layer and tuning the wavelength of the light produced by the laser in response to the refractive index controlled by the electric field applied to the tuning layer;
• a semiconductor layer having a varying thickness, thereby providing a periodic diffraction grating in a resonator length direction of the semiconductor laser;
• a first electrode in electrical contact with the tuning layer for applying a first electric field to the semiconductor tuning layer;
• a second electrode in electrical contact with the semiconductor substrate for injecting current into the semiconductor active layer;
• and
• a third electrode in electrical contact with the tuning layer for applying a second electric field to the semiconductor layer providing the diffraction grating for coupling of the diffraction grating and compensating for light absorption loss caused by application of the first electric field to the tuning layer;
• and
• a fourth electrode commonly used with the first, second, and third electrodes.

A wavelength tunable semiconductor laser device comprising:

• a semiconductor substrate;
• a semiconductor active layer located opposite the semiconductor substrate and producing light in response to current injected into the active layer, the light having a wavelength;
• a semiconductor tuning layer located opposite the semiconductor substrate and having a refractive index that varies in response to an electric field applied to the tuning layer and tuning the wavelength of the light produced by the laser in response to the refractive index controlled by the electric field applied to the tuning layer;
• a first electrode in electrical contact with the tuning layer for applying an electric field to the semiconductor tuning layer;
• a second electrode in electrical contact with the semiconductor substrate for injecting current into the semiconductor active layer;
• and
• a third electrode commonly used with the first applying electrode and second electrodes;
• and
• a light modulator for controlling the light generated in and transmitted through the active layer so that light absorption loss caused by application of an electric field to the tuning layer is compensated.