US 5,686,988 AGranted

Gas concentration measurement instrument based on the effects of a wave-mixing interference on stimulated emissions

AssigneeLockheed Martin Energy Systems, Inc.

InventorW. Ray Garrett

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Abstract

A method and apparatus for measuring partial pressures of gaseous components within a mixture. The apparatus comprises generally at least one tunable laser source, a beam splitter, mirrors, optical filter, an optical spectrometer, and a data recorder. Measured in the forward direction along the path of the laser, the intensity of the emission spectra of the gaseous component, at wavelengths characteristic of the gas component being measured, are suppressed. Measured in the backward direction, the peak intensities characteristic of a given gaseous component will be wavelength shifted. These effects on peak intensity wavelengths are linearly dependent on the partial pressure of the compound being measured, but independent of the partial pressures of other gases which are present within the sample. The method and apparatus allow for efficient measurement of gaseous components.

Claims11

Dependent claims

An apparatus for measuring the concentration of a gaseous component within a sample of a gaseous mixture, said gaseous component being characterizable by a resonance wavelength of highest emission intensity, said apparatus comprising:

(a) at least one tunable laser for providing coherent electromagnetic radiation to said sample, wherein said at least one tunable laser provides resonant excitation of said sample, which said sample then undergoes stimulated emission, the overall process involving an odd number of photons of electromagnetic radiation, said number of photons being greater than one;
(b) at least one resolving device for modifying the electromagnetic radiation produced by said at least one tunable laser such that after the electromagnetic radiation impinges said sample, the intensity of the stimulated electromagnetic radiation emitted by said sample at certain wavelengths will by modified, wherein measured along the forward path of said at least one tunable laser through said sample, the modification of the electromagnetic energy will comprise a shift in wavelengths of the highest intensity peaks and, wherein measured along the forward path of said at least one tunable laser through said sample, and only along the forward path, the modification of the electromagnetic energy will comprise a suppression of intensity at said resonance wavelength of highest emission intensity characteristic of said gaseous component;
and
(c) a detector system for measuring the modifications in wavelengths of said electromagnetic radiation.

1 more element

A method of measuring the concentration of a gaseous component within a sample of a gaseous mixture, comprising:

(a) radiating said sample with sufficient coherent electromagnetic energy to cause at least a portion of said gaseous component to undergo stimulated emission, that is to cause an optically pumped stimulated emission (OPSE) effect to occur within said sample, wherein said radiating step comprises radiating said sample with at least one tunable laser, said radiating step and stimulated emission step together involving a non-unitary odd number of photons of electromagnetic energy;
(b) resolving an emission spectra from said component into the OPSE and non-OPSE portions;
(c) measuring said OPSE portion of said emission spectra, wherein measuring forward along a direction parallel to said laser radiation of said at least one tunable laser, and only along said forward direction, the intensity of said stimulated emission spectra will be suppressed at the resonance wavelengths normally characteristic of said sample, and wherein measuring backwardly along a direction parallel to said laser radiation of said at least one tunable laser, the wavelength of the points of peak intensity of said stimulated emission spectra which are representative of said sample will be shifted.

Dependencies are inferred from the claim text.