Gas laser for emitting light modulated at two different waveleng

Details Gas laser for emitting light modulated at two different waveleng Gas laser for emitting light modulated at two different waveleng

1995-01-25

1996-08-06

Scott, Jr., Leon

Coherent light generators

Particular operating compensation means

372 23, 372 28, 372 98, 372102, 372 20, 372 64, H01S 300

Patent

active

055441866

ABSTRACT:
A gas laser 1 such as a .sup.13 CO.sub.2 -laser emits at two different wavelengths (.lambda..sub.1, .lambda..sub.2) with a sine-shaped adjustment of a resonator mirror or a grating 13 such as a Littrow grating. The gas laser emits radiation at the two desired wavelengths (.lambda..sub.1, .lambda..sub.2) in two mutually adjacent intervals of the resonator length L because of a suitable dimensioning of the grating 13 with respect to grating structure and angle position, the outcoupling factor of the outcoupling mirror 12, the resonator length L and the composition of the gas of the laser. The laser emission is inhibited at the crossover between the two intervals and the sine-shaped modulation (for example with a piezo element) of the resonator length L is essentially symmetrical about this crossover. The invention is also directed to an arrangement for detecting a substance such as NH.sub.3 in a flue gas. This arrangement includes a two wavelengths laser light source 1, a modulation unit 14 and a reference detection unit D1; a transmission optic 2; a measuring path 3 which contains the substance to be detected; a receiving optic 4 and a measuring detector D2. An evaluation apparatus 5 is also provided which determines the ratio of the light absorption in the measuring path 3 at the two wavelengths (.lambda..sub.1, .lambda..sub.2) and determines therefrom the concentration of the substance to be detected in the measuring path 3.

REFERENCES:
patent: 4471220 (1984-09-01), Perry et al.
patent: 4789989 (1988-12-01), Stern et al.
patent: 5002391 (1991-03-01), Wolfrum et al.
patent: 5373525 (1994-12-01), Nowack et al.
"Carbon dioxide laser monitor for NH.sub.3 in flue gas" by A. Stein et al, Applied Optics, vol. 22, No. 21, 1 Nov. 1983, pp. 3378-3381.
"Frequency-switching waveguide CO.sub.2 laser for atmospheric pollution monitoring" by A. Gerasimchuk et al, Sov. J. Quantum Electron, 12(1), published by the American Institute of Physics, Jan. 1982, pp. 110-113.
"Frequency-switching waveguide CO.sub.2 laser for atmospheric pollution monitoring" by A. Gerasimchuk et al, Sov. J. Quantum Electron, vol. 12, No. 1, Jan. 1982, pp. 110 to 112.
"Alternate Intensity Modulation of a Dual-Wavelength He-Ne Laser for Differential Absorption Measurements" by K. Uehara, Applied Physics, vol. 38, (1985), pp. 37 to 40.

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