Abstract
An acousto-optic deflector with a two-element phased-array piezoelectric transducer is investigated at high diffraction efficiency (close to 100%). Significant broadening of the frequency band (and, thus, the angular scanning range) relative to the well-known low efficiency regime is theoretically predicted and experimentally demonstrated. Experiments with an off-axis deflector based on paratellurite (TeO2), a 1.06 µm light radiation and 6 mm interaction length gave frequency band from 17 to 48 MHz at an efficiency of no less than 94% of the maximum value.
Highlights
Phased-array transducers are used to broaden the frequency band and to lower the driving power of acousto-optic (AO) deflectors
The phase shifts between the elements deflect the main lobe of the directivity pattern of the acoustic field, and the Bragg phase-matching can be maintained in a wider frequency band
Phased-array transducers in acousto-optics were described in the 1960s, they are investigated almost only in case of weak AO interaction, under a linear approximation
Summary
Phased-array transducers are used to broaden the frequency band (and, the scanning range) and to lower the driving power of acousto-optic (AO) deflectors. The efficiency is supposed to be proportional to the power of the corresponding component of that spectrum Those investigations show that in case of N transducer elements, each of length L , the spectrum is a product of slowly varying envelope function – it is called the element factor, because it has exactly the shape of the spectrum of the acoustic field, produced by only one element – and a quickly oscillating array factor [1]. The relevance of this work is caused by the application of AO devices in power optics, where constant high diffraction efficiency throughout entire scanning range is needed Another important factor is the development of multichannel signal generators, which made it possible to create any phase shifts and control them precisely
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