IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0653376
(2003-09-02)
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발명자
/ 주소 |
- Riley, Jr.,William J.
- Lutwak,Robert
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
8 인용 특허 :
5 |
초록
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A miniature optical system for use in instruments based on laser spectroscopy of atomic and molecular samples, such as atomic frequency standards and magnetometers. The miniature optical system employs a folded optical path that allows light from a laser diode to pass through the cell twice, reflect
A miniature optical system for use in instruments based on laser spectroscopy of atomic and molecular samples, such as atomic frequency standards and magnetometers. The miniature optical system employs a folded optical path that allows light from a laser diode to pass through the cell twice, reflecting from a mirror and returning to a photodetector co-located with the laser diode. This efficient packaging arrangement allows the laser diode and photodetector to be fabricated on the same semiconductor substrate and allows essentially all of the gas cell volume to be utilized, without additional optical components for collimation. Fabrication of the laser source and detector on a single substrate permits cost-effective batch processing and parallel testing of the key active components.
대표청구항
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What is claimed is: 1. An optical system for interrogating a gaseous sample, comprising a) a semiconductor laser substantially surrounded by a photodetector in a laser/photodetector assembly; b) a reflective surface mounted in opposition to said laser/photodetector assembly, wherein light emitted b
What is claimed is: 1. An optical system for interrogating a gaseous sample, comprising a) a semiconductor laser substantially surrounded by a photodetector in a laser/photodetector assembly; b) a reflective surface mounted in opposition to said laser/photodetector assembly, wherein light emitted by said laser is directed through said gaseous sample at least twice, thereby forming a compact gas interrogation means. 2. The optical system of claim 1 wherein said semiconductor laser and photodetector are co-located on a single substrate. 3. The optical system of claim 1 wherein the semiconductor laser and photodetector are a substantially coplanar assembly and the distance between the substantially coplanar assembly and the reflective surface optimizes the return of light to the photodetector. 4. An optical system of claim 1 wherein the optical system comprises a further reflective surface providing an optical path that traverses said gaseous sample an even number of times that is greater than two. 5. An optical system of claim 1 wherein said semiconductor laser is a vertical cavity surface-emitting laser diode (VCSEL). 6. An optical system of claim 1 wherein said gaseous sample is contained within a sealed gas cell with an optically transparent window. 7. The optical system of claim 6 wherein said sealed gas cell comprises a cup with said reflective surface on its bottom. 8. The optical system of claim 7 wherein said optically transparent window is glass that is anodically bonded to the open end of said cup. 9. The optical system of claim 6 wherein said scaled gas cell comprises a cylinder with a bottom window providing said reflective surface. 10. The optical system of claim 6 wherein said gas cell comprises a cylinder with a glass top and bottom windows that are anodically bonded to the ends of said cylinder, said top glass window carrying said laser/photodetector assembly and said bottom glass window carrying said reflective surface. 11. The optical system of claim 6 wherein said sealed gas cell carries a heater and temperature sensor. 12. The optical system of claim 1 in which said gaseous sample is an atomic gas located between said laser/photodetector assembly and said reflective surface, and in which microwave excitation is additionally introduced into said gaseous sample to resonantly excite the ground state hyperfine transition in interrogating said gaseous atomic sample. 13. The optical system of claim 1 further comprising a quarter-wave plate to circularly polarize the light emission of said semiconductor laser, and in which said gaseous atomic sample is an atomic gas located between said laser photodetector assembly and said reflective surface, the ground-state hyperfine frequency of said gaseous atomic sample being interrogated by means of microwave modulation applied to said laser at an even sub-harmonic thereof. 14. The optical system of claim 1 in which said atomic gaseous sample is located between said laser/photodetector assembly and said reflective surface, and in which audio frequency radiation is resonantly applied to measure magnetic field strength by the technique of Zeeman resonance spectroscopy. 15. In an atomic frequency standard containing an optically reactive gas, the improvement comprising means for providing multiple light paths through said optically reactive gas, including a concentrically assembled semiconductor laser and photodetector and a reflective surface, with a closed gas cell containing said optically reactive gas therebetween, said gas cell having dimensions such that divergent light of said laser optimally impinges on said photodetector. 16. In an atomic magnetometer containing an optically reactive gas, the improvement comprising a means for providing multiple light paths through said optically reactive gas, including concentrically assembled semiconductor laser/photodetector devices and a reflective surface, with a closed gas cell containing the optically reactive gas, therebetween, said gas cell having dimensions such that divergent light of said laser optimally impinges on said photodetector. 17. A gas cell for interrogation of an atomic gas, comprising means forming a closed gas cell containing the atomic gas, said means carrying a light source and a light sensor formed on a single substrate, and further carrying a light reflective surface, said light source, fight reflective surface, and light sensor forming a multiple light path through the atomic gas in said closed gas cell, light from said light source traveling through the closed gas cell and being reflected from said light reflective surface to said light sensor. 18. The gas cell of claim 17 wherein said means forming a closed gas cell comprises a light transparent window carrying said single substrate formed with a laser diode and a photodetector for sensing the emission of the laser diode. 19. The gas cell of claim 18 wherein the means forming the closed gas cell comprises a glass or silicon cup with a cylindrical periphery and a closed end, with said light reflective surface carried by the closed end of said cup. 20. The gas cell of claim 19 wherein the light reflective surface is a mirror formed on the outside of the bottom closed end. 21. The gas cell of claim 17 wherein the means forming a closed gas cell carries a heater. 22. The gas cell of claim 19 further comprising an integrated heater and temperature sensor carried by said closed end. 23. The gas cell of claim 17 wherein the atomic gas comprises cesium gas. 24. The gas cell of claim 17 wherein the atomic gas comprises rubidium gas. 25. A gas cell for interrogation of an atomic gas, comprising means forming a closed gas cell including the atomic gas; an envelope forming the periphery of the gas cell, a transparent window closing one end of the envelope and carrying a substantially coplanar substrate carrying a light source and a light sensing detector, and means closing the other end of the envelope and carrying a light reflective surface said light source, light reflective surface, and light sensing detector forming a multiple light path through the atomic gas in said closed gas cell, light from said light source traveling through the closed gas cell and being reflected from said light reflective surface to said light sensing detector. 26. The gas cell of claim 18 further comprising a quarter wave plate to circularly polarize the light emission of said laser diode. 27. The gas cell of claim 18 further comprising an optical attenuator for the light emission of said laser diode. 28. Means forming a gas cell for an atomic frequency standard, said means comprising a cup-shaped glass container forming the periphery and one end of the gas cell, said one end of the gas cell carrying a light reflective surface, and an integrated heater and temperature sensor, a glass window sealed with the periphery of the cup-shaped glass container, closing and forming the other end of the gas container, a single chip formed with a semiconductor laser diode and a photodetector carried by said glass window, said single chip and said light reflective surface being spaced by said cup-shaped container so light from the semiconductor laser diode can be directed at said light reflective surface and reflected from said light reflective surface to optimally impinge on said photodetector. 29. The means of claim 28 further comprising an optical attenuator and a quarter wave plate positioned between said semiconductor laser diode and the interior of said cup-shaped glass container. 30. In a CPT atomic frequency standard including a closed gas cell containing an atomic gas, the improvement comprising means forming a multiple path for light through the atomic gas, including a concentrically assembled light source and light detector, and a light reflective surface, and a circular polarizer for the light from said light source, said circularly polarized light traveling through the atomic gas in said gas cell and being reflected from said light reflective surface to said light detector. 31. The improvement of claim 30 wherein the light source comprises a semiconductor laser and wherein the semiconductor laser and light detector are a substantially coplanar assembly. 32. The improvement of claim 31 wherein, the semiconductor laser and light detector are formed on a single substrate. 33. The improvement of claim 30 wherein the distance between the concentrically assembled light source and light detector and the light reflective surface optimizes the return of light to the light detector. 34. The improvement of claim 30 wherein the means forming a multiple path through the atomic gas provides an optical path that traverses the atomic gas an even number of times that is greater than two. 35. The improvement of claim 30 wherein said light source comprises a vertical cavity surface-emitting laser diode (VCSEL). 36. The improvement of claim 30 wherein said closed gas cell includes an optically transparent window through which said light travels. 37. The improvement of claim 36 wherein said closed gas cell comprises a cup with said reflective surface on its closed bottom. 38. The improvement of claim 37 wherein said optically transparent window is glass that is anodically bonded to the open end of said cup. 39. The improvement of claim 36 wherein said closed gas cell comprises a cylinder with a bottom window providing said reflective surface. 40. The improvement of claim 30 wherein said closed gas cell comprises a cylinder with glass top and bottom windows that are anodically bonded to the ends of said cylinder, said top glass window carrying said light source and light detector and said bottom glass window carrying said light reflective surface. 41. The improvement of claim 30 wherein said closed gas cell carries a heater and temperature sensor.
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