Detection beyond the standard radiation noise limit using reduced emissivity and optical cavity coupling
First Claim
1. A thermal detector for sensing infrared radiation, the thermal detector comprising:
- a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirror structures; and
an infrared sensor operatively positioned between the first and second thin-film mirror structures and suspended within the resonant optical cavity by one or more support beams so radiation received by the resonant optical cavity impinges on at least a surface portion of the infrared sensor, wherein the infrared sensor is absorption coupled with the resonant optical cavity and the absorption of the infrared sensor varies with direction and wavelength.
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Abstract
The present invention provides thermal detectors having an optical cavity that is optimized to couple light into a sensor. Light that is on resonance is coupled with the sensor with as high as 100% efficiency, while light off resonance is substantially reflected away. Light that strikes the sensor from the sides (i.e. not on the optical cavity axis) only interacts minimally with sensor because of the reduced absorption characteristics of the sensor. Narrowband sensors in accordance with the present invention can gain as much as 100% of the signal from one direction and spectral band, while receiving only a fraction of the normal radiation noise, which originates from all spectral bands and directions.
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Citations
30 Claims
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1. A thermal detector for sensing infrared radiation, the thermal detector comprising:
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a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirror structures; and an infrared sensor operatively positioned between the first and second thin-film mirror structures and suspended within the resonant optical cavity by one or more support beams so radiation received by the resonant optical cavity impinges on at least a surface portion of the infrared sensor, wherein the infrared sensor is absorption coupled with the resonant optical cavity and the absorption of the infrared sensor varies with direction and wavelength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A thermal detector for sensing infrared radiation, the thermal detector comprising:
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a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirror structures, the optical cavity having an optical axis and resonant wavelength; and an infrared sensor operatively positioned between the first and second thin-film mirror structures and suspended within the resonant optical cavity by one or more support beams so radiation received by the resonant optical cavity impinges on at least a surface portion of the infrared sensor, wherein the at least a surface portion of the infrared sensor is absorption coupled with the resonant optical cavity, the absorption of the at least a portion of the infrared sensor varies with direction and wavelength, and wherein the at least a surface portion of the infrared sensor has an absorption less than or equal to twenty-five percent along directions other than the optical axis and at wavelengths other than the resonance wavelength. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method of sensing infrared radiation, the method comprising the steps of:
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providing a resonant optical cavity at least partially defined by first and second spaced apart thin-film mirror structures and an infrared sensor suspended within the resonant optical cavity; causing radiation to enter the resonant optical cavity and absorption couple with the infrared sensor wherein absorption of radiation by the infrared sensor varies with direction and wavelength; and measuring a change in the infrared sensor caused by the radiation coupled with the infrared sensor. - View Dependent Claims (18, 19)
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20. A method of making a thermal detector for sensing infrared radiation, the method comprising the steps of:
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forming a resonant optical cavity at least partially defined by first and second spaced apart thin-film mirror structures; suspending an infrared sensor within the resonant optical cavity; and positioning the infrared sensor within the optical cavity so the infrared sensor is absorption coupled with the resonant optical cavity, the absorption of the infrared sensor varies with direction and wavelength, and the absorption of the resonant wavelength of the optical cavity by the sensor is greater than twenty-five percent. - View Dependent Claims (21, 22, 23)
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24. A thermal detector for sensing infrared radiation, the thermal detector comprising:
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a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirrors and having an optical axis; and an infrared sensor operatively positioned between the first and second thin-film mirrors, the infrared sensor comprising associated physically attached structure wherein the emissivity of the infrared sensor and the physically attached structure is larger by interference along the direction of the optical axis than other directions so the infrared sensor heat transfer is reduced compared to a blackbody. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification