Multi-directional radiation coupling in quantum-well infrared photodetectors
AssigneeCalifornia Institute of Technology
InventorsDaniel W. Wilson, John K. Liu, Sumith V. Bandara, Sarath D. Gunapala
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Abstract
Techniques for coupling radiation into a quantum-well detector by using a two-dimensional array of grating cells to form at least three different grating directions to provide efficient coupling.
Claims21
A device, comprising:
- a detector layer having multiple quantum-well layers and responsive to radiation with a polarization component substantially parallel to said quantum-well layers;
- and
- a grating layer formed over said detector layer to have a two-dimensional array of grating unit cells and to diffract an input beam into at least one diffraction direction not perpendicular to said quantum-well layers, each unit cell shaped to define at least three different grating directions within said grating layer,
- wherein each unit cell includes a central region and a peripheral region conforming to and surrounding said central region,
- wherein central region and said peripheral region have different characteristics to effectuate a phase difference between a light ray reflected from said peripheral region and another light ray reflected from said central region.
A device, comprising:
- at least one quantum-well detector formed of quantum-well layers;
- and
- a grating layer formed over a first side of said detector to have a two-dimensional array of grating cells to diffract an input beam into a least one diffraction direction not perpendicular to said quantum-well layers, each cell being a polygon with at least three pairs of parallel and opposing sides to define at least three different grating directions.
A device, comprising a grating layer having a two-dimensional array of grating cells, each cell being a polygon with at least three pairs of parallel and opposing sides to define at least three different grating directions, wherein each grating cell includes a central region and a peripheral region conforming to and surrounding said central region, which have a difference in their optical thickness values about one quarter of a selected radiation wavelength.
A method, comprising:
- preparing a substrate;
- forming a first contact layer over said substrate;
- forming a detector layer over said first contact layer to include a plurality of quantum-well layers;
- forming a second contact layer over said detector layer;
- patterning said second contact layer to form a periodic array of polygon cells to define at least three grating directions, each cell having a central region and a peripheral region with different characteristics to cause different phase delays in reflecting input light rays;
- and
- removing said substrate from a structure which includes said first contact layer, said detector layer, and said patterned second contact layer.
Dependencies are inferred from the claim text.