Low loss grating for high efficiency wavelength stabilized high power lasers
View Patent ↗A low optical loss and high efficiency grating is placed within a broad-area high-power laser diode or single spatial mode laser diode to narrow the spectral width and stabilize the emission wavelength. Several embodiments of grating configurations are presented, together with the measured results of a reduction to practice of a particular embodiment.
1. A semiconductor pump laser comprising:
a semiconductor chip having a first facet at one end thereof and a second facet at the opposite end thereof;
an optical waveguide between the first facet and the second facet, comprising an active layer sandwiched between a n-type layer and a p-type layer to form a diode, wherein the optical waveguide and the first and second facets form an optical cavity capable of supporting multiple lasing modes, wherein the cavity has a cavity length that is between about 800 micron and 3000 micron;
a single metal electrode in contact with a p-side current injection area extending along the optical waveguide for pumping a drive current into a pumped area of the active layer;
a grating extending from the first facet to the second facet within the waveguide to provide distributed feedback for a plurality of adjacent lasing modes, wherein the grating is coupled to the active layer at a total coupling coefficient—cavity length product not exceeding 0.2.
2. The semiconductor pump laser as defined in claim 1 wherein the grating partially overlaps the pumped area.
3. The semiconductor pump laser as defined in claim 1 wherein the grating is divided into more than one non-contiguous segment.
4. The semiconductor pump laser as defined in claim 1 wherein the grating is a first order grating.
5. The semiconductor pump laser as defined in claim 1 wherein the cavity is made of compound semiconductor.
6. The semiconductor pump laser as defined in claim 5 wherein the compound semiconductor is a combination of one or more of aluminum, gallium, and arsenic.
7. The semiconductor pump laser as defined in claim 6 wherein the emission wavelength is between about 790 nm and 1000 nm.
8. The semiconductor pump laser as defined in claim 1 wherein the grating comprises corrugations that have a uniform pitch.
9. The semiconductor pump laser as defined in claim 1 wherein the grating comprises corrugations that have a non-uniform pitch.
10. The semiconductor pump laser as defined in claim 1 wherein the grating comprises corrugations that are curved.