Tunable laser with directional coupler

A laser comprising:

• an output;
• a first reflective element;
• a second reflective element;
• a gain medium between the first reflective element and the second reflective element;
• a coupler between the first reflective element and the second reflective element, the coupler comprising:
• a first port;
• a second port;
• and
• a third port;
• a first waveguide optically coupling the first port with the gain medium;
• a second waveguide optically coupling the second port with the second reflective element;
• and
• a third waveguide optically coupling the third port with the output.

A method for using a directional coupler to output light from a lasing cavity, the method comprising:

• generating light with a gain medium;
• guiding light from the gain medium to a first reflective element;
• guiding light from the gain medium to a first port of a coupler;
• guiding light from a second port of the coupler to a second reflective element;
• and
• guiding light from a third port of the coupler to an output of a laser.

A directional coupler for providing output of a semiconductor laser, the directional coupler comprising:

• a substrate;
• a cladding;
• a core, wherein:
• the cladding is between the substrate and the core;
• and
• the core forms:
• a first port optically coupled with a gain medium;
• a second port optically coupled with a reflective element;
• and
• a third port optically coupled with a laser output.