Selection of modulation type in acousto-optic delay line with direct detection

Abstract

This paper presents the physical and mathematical interpretation for the sequence of the response formation at the output of the acousto-optic delay line direct detection for various forms of connected to the terminals electro-acoustic transducer of high-frequency vibration. It has been shown that for the chosen design the intensity of light, which is incident on the photosensitive surface of the photodetector, varies only in the case of a change of acoustic power in the photoelastic medium. This eliminates the possibility of using the angular modulation for the transfer of video signal spectrum in the range of operating frequencies of the acousto-optic modulator in acousto-optic delay line with direct detection. In order to provide such a possibility it is recommended to install on the path of the deflected light a reference indicator, which converts the changes in the angle of diffraction into corresponding changes in the intensity of light, which is incident on the photosensitive surface of the photodetector. The proposed design is investigated for square and circular apertures of the light beam. It has been determined that best results are achieved in the case of the light beam with a square aperture and with a uniform distribution of power flow therein. We present the main results of experimental studies that confirm the effectiveness of the proposed design.