External cavity semiconductor laser and method for fabrication thereof
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 - 4 . (canceled)
5 . A microfabricated etalon, comprising:
a crystalline substrate having first and second opposing surfaces;
a spacer layer disposed over the first surface of the substrate, the spacer layer having an exterior surface;
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 first interference filter disposed over the exterior surface of the spacer layer and a second interference filter disposed over the exposed portion of the spacer layer to provide an etalon between the interference filters.
6 . An external cavity semi-conductor laser, comprising:
a laser gain medium for providing a source of optical radiation;
an external optical cavity disposed in optical communication with the gain medium, the cavity dimensioned sufficiently short to permit a single wavelength selective device to select and sustain a single longitudinal lasing mode; and
a single wavelength selective device disposed in the external optical cavity to select and sustain a single longitudinal lasing mode.
7 . An external cavity semi-conductor laser according to claim 6 , wherein the wavelength selective device comprises a microfabricated etalon.
8 . An external cavity semi-conductor laser according to claim 7 , wherein the etalon comprises a variable space gap adjustable from a first dimension to a second dimension to provide for lasing at a first longitudinal mode or a second longitudinal mode.
9 . An external cavity semi-conductor laser according to claim 8 , wherein the etalon comprises an electrode disposed proximate the gap for providing a repulsive or attractive force to change the gap spacing.
10 . An external cavity semi-conductor laser according to claim 6 , wherein the wavelength selective device comprises single crystal silicon.
11 . An external cavity semi-conductor laser according to claim 6 , wherein the wavelength selective device comprises:
a crystalline substrate having first and second opposing surfaces;
a spacer layer disposed over the first surface of the substrate, the spacer layer having an exterior surface;
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 first interference filter disposed over the exterior surface of the spacer layer and a second interference filter disposed over the exposed portion of the spacer layer to provide an etalon between the interference filters.