Method, system and apparatus for higher order mode suppression

1. A laser diode, comprising:

a transverse waveguide that is orthogonal to the lateral waveguide comprising an active layer between an n-type waveguide layer and a p-type waveguide layer, wherein the transverse waveguide is bounded by an n-type cladding layer on an n-side and p-type cladding layer on a p-side; and

a lateral waveguide bounded in a longitudinal direction at a first end by a high reflector (HR) coated facet and at a second end by a partial reflector (PR) coated facet, the lateral waveguide further comprising a buried higher order mode suppression layer (HOMSL) disposed beneath the p-cladding within the lateral waveguide or on one or both sides of the lateral waveguide or a combination thereof, wherein the HOMSL extends in a longitudinal direction from the HR facet a length less than the distance between the HR facet and the PR facet.

2. The laser diode of claim 1 , wherein the refractive index of the HOMSL disposed on one or both sides of the lateral waveguide is higher than the p-type waveguide layer and the p-cladding layer.

3. The laser diode of claim 1 , wherein the refractive index of the HOMSL disposed within the lateral waveguide is lower than the n-type waveguide layer or the p-type waveguide layer or a combination thereof.

4. The laser diode of claim 1 , wherein a thickness of the HOMSL is selected based on a magnitude of the refractive index contrast in the lateral waveguide induced by thermal lensing within the lateral waveguide during operation of the laser diode.

5. The laser diode of claim 4 , wherein the thickness of the HOMSL is further selected to reduce the magnitude of the refractive index contrast of the lateral waveguide during operation.

6. The laser diode of claim 5 , wherein the magnitude of the refractive index contrast is in the range of 10-5<Δn<10-3.

7. The laser diode of claim 5 , wherein the lateral waveguide supports fewer than ten lateral modes.

8. The laser diode of claim 5 , wherein the lateral waveguide supports a single lateral mode.

9. The laser diode of claim 1 , wherein a thickness of the HOMSL is selected to reduce an effective index on a side of the lateral waveguide extending from the HR facet.

10. The laser diode of claim 1 , wherein the HOMSL comprises gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), indium aluminum gallium arsenide (InAlGaAs), indium gallium phosphide (InGaAsP).

11. The laser diode of claim 1 , wherein the lateral waveguide is bounded in the lateral direction by a ridge waveguide wherein the ridge waveguide extends from the HR facet to the PR facet.

12. The laser diode of claim 2 , wherein the HOMSL laterally overlaps the lateral waveguide by between 0-10 um on either side, or 0-20 um total.

13. The laser diode of claim 3 , wherein the HOMSL disposed within the lateral waveguide is narrower laterally than the lateral waveguide by 0-10 um on either side or 0-20 um total.

14. The laser diode of claim 1 , wherein the lateral waveguide is bounded in the lateral direction by a ridge waveguide in the longitudinal direction from the PR facet a length less than the distance between the PR facet and the HR facet.

15. The laser diode of claim 1 , wherein the transverse waveguide thickness in the active stripe is reduced by either etching down or selectively depositing thicker layers adjacent to an active stripe.

16. The laser diode of claim 1 , wherein a thinner low index layer is disposed along the width of the lateral waveguide in a region of the HOMSL.