DBR laser with improved thermal tuning efficiency

1. A laser comprising:

a base substrate comprising a semiconductor material;

a gain medium embedded in the base substrate;

a waveguide positioned above the base substrate in optical communication with the gain medium and defining a gap extending between the base substrate and the waveguide along a substantial portion of the length thereof, the waveguide having a grating formed there on;

pillars comprising a thermal insulative semiconductor material extending between the waveguide and the base substrate;

at least one heating element in thermal contact with the waveguide; and

a controller electrically coupled to the at least one heating element and configured to adjust optical properties of the waveguide by controlling power supplied to the at least one heating element.

2. The laser of claim 1 , wherein the gap extends along a majority of the length of the waveguide.

3. The laser of claim 1 , wherein the reflector is a distributed Bragg reflector and wherein the gap extends along a majority of the length of the distributed Bragg reflector.

4. The laser of claim 3 , wherein the gap extends along 90 percent of the length of the grating.

5. The laser of claim 3 , wherein the distributed Bragg reflector comprises a sampled grating having discrete grating regions separated from one another.

6. The laser of claim 5 , wherein the heating element comprises heaters each positioned over one of the discrete gratings.

7. The laser of claim 6 , further comprising discrete metal areas extending over the distributed Bragg reflector between the heating elements.

8. The laser of claim 7 , wherein the discrete metal areas comprise gold and wherein the heating elements comprise platinum.

9. The laser of claim 1 , wherein the waveguide is formed in a raised substrate, the raised substrate having a lower surface, the base substrate and lower surface defining the gap between the raised substrate and the base substrate, the raised substrate further comprising exposed lateral surfaces perpendicular to the lower surface.

10. The laser of claim 1 , wherein the pillars comprise InGaAsP.

11. The laser of claim 1 , wherein the pillars comprise 1.3Q InGaAsP.

12. A laser comprising:

a base substrate comprising a semiconductor substrate;

a gain medium formed on the base substrate;

a raised substrate having a first end and a second end and having a top surface, bottom surface, and lateral surfaces extending between the top and bottom surfaces, the first end located adjacent the gain medium, the lower surface and base substrate defining a gap along a majority of a distance between the first and second ends, the top and lateral surfaces being exposed.

a waveguide embedded in the raised substrate in optical communication with the gain medium, the waveguide having a reflector formed therein;

at least one heating element in thermal contact with the waveguide;

a plurality of pillars comprising an insulative semiconductor material extending between the base substrate and the raised substrate, the at least one pillars having a combined width parallel to a line extending between the first and second ends that is less than 90 percent of a length of the raised substrate between the first and second ends; and

a controller electrically coupled to the at least one heating element and configured to adjust optical properties of the waveguide by controlling power supplied to the at least one heating element.

13. The laser of claim 12 , wherein the at least one pillars include a plurality of pillars;

wherein the at least one heating element comprises a plurality of heating elements; and

wherein each heating element of the plurality heating elements is positioned at a midpoint between adjacent pillars of the plurality of pillars.

14. The laser of claim 1 , wherein each of the at least one heating elements is positioned at a midpoint between adjacent pillars.