Optics: measuring and testing – By shade or color
Patent
1979-09-14
1981-10-27
Evans, F. L.
Optics: measuring and testing
By shade or color
356300, 356432, G01N 2127
Patent
active
042970350
ABSTRACT:
A method and device for detecting a narrow spectral feature in a sample is described. The method includes the steps of providing a beam of light having an optical frequency bandwidth which is narrow compared to the width of the narrow spectral feature and having a center frequency .omega..sub.C which lies near the narrow spectral feature, phase modulating the beam of light with a single RF frequency to provide a pure FM spectrum having upper and lower sidebands, exposing the sample containing the narrow spectral feature to the modulated light so that only one of the FM sidebands probes the narrow spectral feature, photodetecting the light emerging from the sample to detect a RF beat at the specific RF frequency used for phase modulation, and electronically monitoring the amplitude of the RF beat signal to indicate the strength of the narrow spectral feature. A preferred embodiment of this invention is a multiplex readout device for hole burning memories. The device includes means for using a frequency modulated laser light with widely spaced sidebands arranged so that only one of each pair of upper and lower sidebands probes the frequency location of each hole. The device uses many simultaneous RF frequencies to drive the phase modulator and produce the light with FM sidebands which simultaneously probes all the hole locations of interest. The device includes photodetection means to receive the light after it has passed through the sample and phase sensitive multiplex analyzing means to process the electrical signals from the photodetection means to indicate the presence or absence of holes.
REFERENCES:
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patent: 3899430 (1975-08-01), Ancker-Johnson
patent: 3975628 (1976-08-01), Graves et al.
patent: 4142773 (1979-03-01), Avramenko et al.
patent: 4146783 (1979-03-01), Desbois et al.
Harris et al., Applied Physics Letter, vol. 7, No. 7, Oct. 1, 1965, pp. 185-187.
Tang et al., Journal of Applied Physics, vol. 45, No. 10, Oct. 1974, pp. 4503-4505.
Evans F. L.
International Business Machines - Corporation
Kieninger Joseph E.
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