System and method for gas analysis using doubly resonant photoacoustic spectroscopy
First Claim
1. A doubly resonant photaoacoustic gas detector comprising:
- i) a continuous wave external light source for generating a light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte;
ii) a closed path optical cavity having at least two reflective surfaces;
iii) an acoustic resonator chamber, said acoustic resonator chamber being contained within said optical cavity, and comprising;
a) an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, b) a first entrance port for admitting light from said external light source into said chamber, c) a second port which passes said light out of said chamber after transmission of said light through said first port and said chamber, whereby the light beam generated by said external light source passes sequentially into, through and out of said chamber, said light beam being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.
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Abstract
A method for analyzing gas concentration using doubly resonant photoacoustic spectroscopy, and a doubly resonant photaoacoustic gas detector comprising: i) a continuous wave light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte; ii) a closed path optical cavity having at least two reflective surfaces; iii) an acoustic resonator chamber contained within said optical cavity, and comprising an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, the light beam passing sequentially into, through and out of said chamber, and being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.
62 Citations
30 Claims
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1. A doubly resonant photaoacoustic gas detector comprising:
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i) a continuous wave external light source for generating a light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte;
ii) a closed path optical cavity having at least two reflective surfaces;
iii) an acoustic resonator chamber, said acoustic resonator chamber being contained within said optical cavity, and comprising;
a) an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, b) a first entrance port for admitting light from said external light source into said chamber, c) a second port which passes said light out of said chamber after transmission of said light through said first port and said chamber, whereby the light beam generated by said external light source passes sequentially into, through and out of said chamber, said light beam being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method for analyzing gas concentration using doubly resonant photoacoustic spectroscopy, comprising the steps of:
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containing a gas sample in an acoustic resonator contained within a resonant external optical cavity;
exciting the gas sample with a beam of excitation light having a wavelength where the gas being analyzed has an absorption feature;
said beam of excitation light being reflected back and forth through said gas sample by at least two reflecting surfaces of said resonant external optical cavity;
oscillating at least one of the reflecting surfaces over a distance such that the external optical cavity tracks the excitation beam'"'"'s full excursion in wavelength space of 1.1 times the full width at half maximum of the absorption feature of said sample gas.
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Specification