Multiple band frequency locking in acousto-optic system with optoelectronic feedback

In this paper, we introduce and analyze both experimentally and theoretically multiple-band frequency locking, which becomes possible in an acousto-optic (AO) system with optoelectronic feedback. This effect is observed in a system combining a collinear AO cell and positive electronic feedback. The feedback signal is formed with the optical heterodyning effect, which occurs at the AO cell output and takes place in the special regime of collinear AO diffraction. It is shown for the first time, to the best of our knowledge, that frequency locking is possible in this system when connecting an external RF generator not only in one band near the self-oscillation frequency, but in several bands. The existence of as many as nine frequency-locking bands is predicted. The number of frequency-locking bands and their widths depend on the feedback gain and RF generator signal magnitude.