Optics: measuring and testing – For light transmission or absorption
Patent
1980-02-29
1981-12-01
Rosenberger, R. A.
Optics: measuring and testing
For light transmission or absorption
250351, G01N 2101
Patent
active
043033431
ABSTRACT:
Method and apparatus for high-sensitivity (.alpha..ltorsim.10.sup.-6 cm.sup.-1) optoacoustic (OA) spectroscopy of substantially transparent bulk condensed matter. Part of the sample to be investigated is irradiated by pulses of radiation, typically from a pulsed dye laser. The small amount of energy absorbed by the sample causes thermal expansion of the irradiated region, resulting in cylindrical stress waves being radiated from that region. These stress waves can be observed with appropriate detection means at a location remote from the source. The method is applicable to essentially transparent liquids, and solids, and to absorptive solids suspended in liquids, and the like. Possible choices of probe radiation are not only the conventional ones of visible, near UV, and near infrared electromagnetic radiation, but also, for instance, .gamma.-rays, x-rays, vacuum UV, and far infrared. Two conditions are shown to exist that relate pulse duration, beam size, and various material parameters, observation of which results in optimization of the sensitivity of the method, and the sensitivity is typically highest for pulses having duration of about 10.sup.-7 sec-10.sup.-4 sec.
REFERENCES:
patent: 3948345 (1976-04-01), Rosencwaig
Hordvik et al., "Photoacoustic Technique for Determining Optical Absorption Coefficients in Solids", Applied Optics, vol. 16, No. 1, Jan. 1977, pp. 101-107.
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Gutfeld et al., "20-MHz Acoustic Waves From Pulsed Thermoelastic Expansions of Constrained Surfaces", Applied Physics Letters, vol. 30, No. 6, Mar. 15, 1977, pp. 257-259.
Tam et al., "Ultimate Corrosion Resistant Optoacoustic Cell for Spectroscopy of Liquids", Optics Letters, vol. 5, No. 1, Jan. 1980, pp. 27-29.
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Patel Chandra K. N.
Tam Andrew C.
Bell Telephone Laboratories Incorporated
Rosenberger R. A.
Wilde Peter V. D.
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