DBR laser with improved thermal tuning efficiency

1. A laser comprising:

a base substrate;

a gain medium deposited on the base substrate;

a waveguide positioned above the base substrate in optical communication with the gain medium, the waveguide having a grating formed therein and defining a gap extending between the base substrate and the waveguide along an entire length of the grating;

a heating element in thermal contact with the waveguide; and

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

2. The laser of claim 1 , wherein the gap is filled with a gas.

3. The laser of claim 1 , further comprising a plurality of supports positioned adjacent the waveguide and extending between the waveguide and the base substrate.

4. The laser of claim 3 , wherein the plurality of supports are positioned on either side of the waveguide.

5. The laser of claim 3 , wherein the plurality of supports are positioned on either side of the gap.

6. The laser of claim 1 , wherein the supports comprise a SiO 2 film.

7. The laser of claim 1 , wherein the supports comprise InP.

8. The laser of claim 1 , wherein the waveguide is embedded within a raised substrate having a lower surface and lateral surfaces perpendicular to the lower surface, the lower surface and the base substrate defining a gap extending along the entire length of the grating.

9. The laser of claim 8 , wherein the supports comprise a SiO 2 film extending between the lateral surfaces of the raised substrate and the base substrate.

10. The laser of claim 9 , wherein the heating element comprises a first heating element, the laser further comprising a second heating element, the second heating element positioned between the first heating element and the gain section and having a length substantially shorter than that of the first heating element.

11. The laser of claim 10 , wherein the controller is electrically coupled to the second heating element and is configured to cause the second heater to produce heat at a rate per unit length greater than the first heating element.

12. The laser of claim 11 , wherein the second heating element has a length less than 10% that of the first heating element.

13. The laser of claim 12 , wherein the second heating element has a length less than 5% that of the first heating element.

14. The laser of claim 11 , wherein the controller is configured to supply power to the second heating element at a rate per unit length greater than twenty times the rate per unit length that the controller is configured to supply power to the first heating element.

15. A laser comprising:

a base 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;

lateral supports engaging the lateral surfaces and extending to the base substrate;

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

a heating element in thermal contact with the waveguide; and

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

16. The laser of claim 15 , wherein the lateral supports are disposed on either side of the raised substrate.

17. The laser of claim 15 , wherein the lateral supports comprise a SiO 2 film.