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US 6,271,526 B1Granted
Efficient radiation coupling to quantum-well radiation-sensing array via evanescent waves
AssigneeCalifornia Institute of Technology
InventorsThomas Cwik, Cavour Yeh
Life of this patent
Estimating the term…
Abstract
Devices and techniques for using a prism to couple IR radiation to a quantum-well sensor with a polarization substantially perpendicular to the quantum-well layers.
Claims19
A semiconductor device, comprising:
- a semiconductor substrate having a sensing region that has a quantum-well structure of alternating semiconductor layers parallel to said substrate to absorb radiation at or near a resonance wavelength, and a non-sensing region that at least partially encloses said sensing region to form a resonant optical cavity whose optic axis is parallel to said substrate;
- and
- a prism engaged to said substrate over said sensing region, said prism having a flat surface substantially parallel to and spaced from said substrate by an air gap less than one wavelength of the radiation to permit evanescent coupling to said sensing region, and a slanted surface forming a desired angle with respect to said flat surface to couple radiation to said flat surface at an incident angle that is equal to or greater than a critical incident angle that would cause a total internal reflection at said flat surface,
- wherein a resonance peak of said optical cavity substantially overlaps with said resonance wavelength of said sensing region.
1 more element
A semiconductor device, comprising:
- a substrate formed of a semiconductor material and having a first surface and a second surface opposing said first surface;
- a quantum-well sensing region in said substrate, having alternating semiconductor layers of two different compositions that are substantially parallel to said first and second surfaces and absorb radiation at or near a resonance wavelength that is polarized perpendicular to said semiconductor layers;
- a non-sensing region in said substrate, having an index of refraction different from an index of refraction of said sensing region, to at least partially enclose said sensing region to form a resonant optical cavity whose optic axis is parallel to said semiconductor layers;
- a conductive layer formed over said second surface to supply an electrical potential to said sensing region;
- a dielectric layer formed over said first surface with a thickness less than one wavelength of the radiation;
- and
- a prism engaged to said substrate over said sensing region and comprising:
- a flat surface in contact with said dielectric layer, and
- a slanted surface forming a desired angle with respect to said flat surface to couple radiation to said flat surface at an incident angle equal to or greater than a critical angle for a total internal reflection to cause an evanescent wave to propagate parallel to said first surface in said sensing region.
6 more elements
A method for detecting radiation by using a semiconductor quantum-well sensor, comprising:
- projecting a beam of radiation towards a quantum-well sensor in a direction substantially perpendicular to quantum-well layers;
- using a first surface of a prism to receive the beam and a second surface of the prism to receive the beam from the first surface at an incident angle equal to or greater than a critical angle for a total internal reflection so as to produce an evanescent wave propagating along said second surface, wherein the beam is at least partially polarized in an incident plane that is defined by the direction of the beam and a normal direction of the second surface;
- and
- placing the quantum-well sensor near said second surface by a distance less than one wavelength of the radiation to couple radiation energy of the evanescent wave into the quantum-well sensor so that at least a portion of the evanescent wave in the quantum-well sensor is polarized perpendicular to the quantum-well layers.
1 more element
Dependencies are inferred from the claim text.