About measurement of the spectral distribution of optical radiation by acousto-optical spectrometers

V.I. Pustovoit

Al’manac of Modern Metrology № 4 (16) 2018, pages 15–32

A new method of spectral measurements of incoming optical radiation based on collinear acousto-optic filters which is based on sequential diffraction of incident polarized optical radiation using two sound packets of the same frequency and with the same initial phases is proposed. A theory of diffraction of optical radiation on two consecutive packets of sound waves propagating in a crystal was constructed, and the instrumental function of the AO spectrometer was found. It is shown that the instrumental function of such an acousto-optic spectrometer becomes time-dependent, with the frequency of this dependence, in its turn, depends on the intensity of the sound wave, on the tuning from synchronism conditions and other optical and acoustic properties of the crystalline medium. Measuring the time dependence of the photocurrent allows you to determine the spectral quality of the incident optical radiation with greater accuracy, since the noises with this method of measurement makes a smaller contribution to the value of the photocurrent. The dependence of the measured photocurrent on the frequency for a multiple sequence of sound packets was found explicitly and it was shown that measuring the frequency dependences of the photocurrent allows determining not only the spectral composition of the incident optical radiation, but also some properties of the photodetector.

Key words: acousto-optics, diffraction of light on sound, methods of spectral measurements, methods of light radiation modulation.

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