Experimental examination of frequency locking effect in acousto-optic system

Collinear Acousto-Optic Filtration With Electronically Adjustable Transmission Function

“…6 where the I 0 transmission function passband narrowing and AO diffraction efficiency dependences on RF generator acoustic power obtained for three various gain values are presented. The highest I 0 transmission function narrowing that was observed experimentally was 74 times, unfortunately as for I 1 component [24] the narrowing is accompanied by the decrease of AO diffraction efficiency from 95% till 6%.…”

“…In this paper we consider how the introduction of an optoelectronic feedback loop affects the operation and characteristics of the collinear AO filter and what additional possibilities for controlling the optical radiation spectral composition appear in this case. The results of the similar system study presented earlier in [24]- [27] has shown that changing the feedback parameters it is possible to control the width of the AO filter transmission function and suppress its side lobes.…”

“…A distinctive feature of this AO system from the previously examined [24]- [27] is that the beamsplitter is mounted before of the output polarizers. The polarization plane of the input polarizer is oriented orthogonally to Y crystallographic axis.…”

“…The second beam will pass through the analyzer, with the polarization plane oriented at an angle β = 45°to the Y axis (the case of maximal I 1 component). Thus, its intensity will be modulated by amplitude with the ultrasound frequency, excited in the AO cell [24]- [27], [33], which makes it possible to use it for signal generation at the feedback circuit input, so we will call it the feedback beam.…”

“…In the previous studies considering only the feedback beam it was shown that the system has several operating modes depending on the feedback gain factor κ magnitude [24], [25]. At relatively low gain values, the system behave like a conventional AO filter -the central transmission wavelength can be tuned by varying the RF generator frequency.…”