External cavity semi-conductor laser and method for fabrication thereof
View Patent ↗The present invention concerns a design for an external cavity single mode laser wherein a short optical path length for the optical cavity (e.g., ˜3 to 25 mm) provides sufficient spacing of the longitudinal modes allowing a single wavelength selective element, such as a microfabricated etalon, to provide a single mode of operation, and optionally a selectable mode of operation.
1. A method for fabricating a microfabricated etalon, comprising:
providing a crystalline substrate having first and second opposing surfaces;
providing a spacer layer over the first surface of the substrate, the spacer layer having an exterior surface;
forming a hole extending through the substrate from the first surface to the second surface, the hole having a base adjacent an exposed portion of the spacer layer and a sidewall;
providing a first interference filter over the exterior surface of the spacer layer and providing a second interference filter over the exposed portion of the spacer layer and the sidewall; and
removing a portion of the spacer layer proximate the hole to provide a gap between the interference filters to provide an etalon between the interference filters.
2. A method for fabricating a microfabricated etalon according to claim 1 , comprising providing a conductive electrode proximate the gap, the electrode configured to provide a repulsive or attractive force to change the gap spacing.
3. A method for fabricating a microfabricated etalon according to claim 1 , wherein the forming of the hole comprises anisotropically etching the substrate.
4. A method for fabricating a microfabricated etalon according to claim 2 , wherein the conductive electrode is disposed over the first interference filter.
5. A method for fabricating a microfabricated etalon according to claim 4 , wherein the conductive electrode comprises a plurality of conductive electrodes over the first interference filter.
6. A method for fabricating a microfabricated etalon according to claim 4 , further comprising forming a conductive electrode over the second interference filter.
7. A method for fabricating a microfabricated etalon according to claim 4 , wherein the crystalline substrate is a silicon substrate.
8. A method for fabricating a microfabricated etalon according to claim 1 , wherein the portion of the spacer layer is removed by etching through the spacer layer in a direction from the exterior surface.
9. A method for fabricating a microfabricated etalon according to claim 8 , further comprising forming a plurality of holes in the first interference layer to expose the exterior surface of the spacer layer, wherein the portion of the spacer layer is removed by etching through the plurality of holes.