Wavelength tunable filter and wavelength tunable laser module

A wavelength tunable filter comprising:

• a semiconductor substrate;
• a first optical waveguide which is mounted on the semiconductor substrate and provided with a first core layer;
• and
• a second optical waveguide which is mounted on the semiconductor substrate and provided with a second core layer;
• the first optical waveguide and the second optical waveguide being positioned parallel to each other in plane,
• wherein a grating is formed in one or more of the optical waveguides;
• wherein the first core layer is positioned close to a p-type conductive semiconductor and an n-type conductive semiconductor and structured to be capable of injecting a current or applying a voltage;
• and
• wherein the second core layer is positioned close to either the p-type conductive semiconductor or the n-type conductive semiconductor.

A wavelength tunable filter comprising:

• a semiconductor substrate having a first-type conductive semiconductor layer;
• a first optical waveguide;
• and
• a second optical waveguide;
• the first optical waveguide and the second optical waveguide being extended from a first side of the semiconductor substrate to an opposing second side thereof,
• wherein the first optical waveguide includes
• a first grating,
• a first core layer placed over the first-type conductive semiconductor layer,
• a first electrode placed under the first-type conductive semiconductor layer,
• a second-type conductive semiconductor layer placed over the first core layer, and
• a second electrode placed over the second-type conductive semiconductor layer;
• and
• wherein the second optical waveguide includes
• a second core layer placed over the first-type conductive semiconductor layer, and
• an insulating film placed between the second core layer and the second electrode.