Multi-directional radiation coupling in quantum-well infrared photodetectors
First Claim
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1. 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.
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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.
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Citations
21 Claims
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1. A device, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 20)
a reflective layer directly formed over said grating layer; and
a transparent layer formed on one side of said detector layer opposing an opposite side that has said grating layer.
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9. The device as in claim 8, wherein both of said reflective layer and said transparent layer are electrically conductive to couple an electric bias to said detector layer.
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20. The device as in claim 1, wherein said multiple quantum-well layers include GaAs.
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10. A device, comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15, 21)
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- 16. 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.
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19. A method, comprising:
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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.
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Specification