Westinghouse Electric Corporation

Lyle H Taylor

William H Kasner

Milton S Gottlieb

Nathan T Melamed

Kenneth B Steinbruegge

Johanna S Schruben

Gases such as pollutants are discerned in a sample, preferably using a laser to emit an infrared light beam along a sight path for illuminating the gases. The beam is directed along the sight path and collects light from the gases. An optical tunable filter selects a particular optical wavelength or band, and the filtered wavelength is focused on a detector coupled to an analyzer. The analyzer can include a processor that can pulse the laser or coordinate collection of data from sample gases and from a reference cell containing known gases, e.g., using an optical chopper wheel. The processor analyzes the light levels as a function of wavelength to discriminate for the presence of selected gases by determining a characteristic pattern of light absorption and light emission by the gases. The tunable filter has an acousto-optical crystal of Tl.sub.3 AsSe.sub.3, in which an RF acoustic wave is generated for varying diffraction of light by the filter, thereby selecting a wavelength. A nonlinear output crystal can in inserted controllably to selectively generate harmonics for increasing wavelength coverage, and can also be Tl.sub.3 AsSe.sub.3. A broad band infrared illumination source can be used. When the infrared excitation beam is off, the filter acts on infrared emissions of the gases. Sensitivity to narrow emission lines is increased by modulating the RF drive to the tunable filter, producing derivatives of the spectra.

Hazardous air pollutants monitor

Gases such as pollutants are discerned in the open air, preferably using a laser to emit an infrared light beam along a sight path for illuminating the gases. A telescope is directed along the sight path and collects light from the gases, the combination of the laser and telescope permitting redirection of the sight path to any target, such as fugitive emissions of a stack. An optical tunable filter is coupled to the telescope for selecting a particular optical wavelength or band, and focusing the filtered wavelength on a detector. A processor 72) is coupled to the detector output and pulses the laser. The processor analyzes the light levels as a function of wavelength to discriminate for the presence of selected gases by determining a characteristic pattern of light absorption and light emission by the gases. The tunable filter has an acousto-optical crystal of Tl.sub.3 AsSe.sub.3, in which an RF acoustic wave is generated for varying diffraction of light by the filter, thereby selecting a wavelength. A nonlinear output crystal selectively generates harmonics for increasing wavelength coverage, and can also be Tl.sub.3 AsSe.sub.3. When the laser is off, the filter acts on infrared emissions of the gases. Sensitivity to narrow emission lines is increased by modulating the RF drive to the tunable filter, producing derivatives of the spectra.

Remote hazardous air pullutants monitor

A source of broad-band and/or narrow band optical radiation is detected and identified by apparatus including a pair of acousto-optical tunable filters which diffract from orthogonally polarized components of the optical radiation, a diffracted ordinary polarized beam and diffracted extraordinary beam, respectively. Undiffracted polarized radiation from the two AOTFs is combined and directed to a first detector which may comprise a small array such as a quadrant array. The diffracted ordinary and extraordinary polarized beams are directed to a second detector which is preferably a single large imaging array. A signal processor uses signals from the first detector generated by the undiffracted beams to detect the presence of the source, and polarized spectral signals from the large imaging array to identify the source of the radiation . A control unit generates radio frequency signals which can be rapidly varied in frequency to control wavelength of the polarized beams diffracted by the AOTFs. These radio frequency (rf) signals may be applied simultaneously, with or without amplitude modulation, or sequentially, to the AOTFs, and may be of the same or different frequencies. The rf drive may be withheld from the AOTFs to maximize the undiffracted beams for maximum range detection.

Acousto-optic tunable filter apparatus and method for detecting and

The operation of a two-photon, three level laser system at high temperatures or pressures is made possible by reducing the build up time of the flux of the second lasing transition in the laser discharge region.

Operation of a two-photon three level laser

A broadband antireflection multilayer coating for infrared transmissive materials comprises a first thin film layer selected from the group consisting of zinc-selenide and zinc-sulfide, a second thin film layer selected from the group consisting of lead-fluoride and aluminum oxide and a third thin film layer selected from the group consisting of magnesium-fluoride, barium-fluoride and calcium-fluoride. This antireflection coating is particularly useful with acousto-optic tunable filter systems, wire grid polarizers and infrared frequency doublers.

Broadband antireflection coating for infrared transmissive materials

Multiple input laser pulses, wherein each pulse serves to create the population inversion for the next pulse, are amplified in the laser medium of a single laser amplifier apparatus.

Technique for amplifying two or more laser beams in a single laser

Stimulated emission resulting from a secondary source of radiation transfers population from a lower laser level of a primary lasing transition to a third energy level which is not involved in the primary lasing of a laser system to reduce lower laser level bottlenecking.

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Murrysville, PA, United States of America

Lyle H Taylor