29 September 2005 Functional improvements in some of acousto-optic devices by means of preliminary dynamic signal pre-distortions
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Abstract
All acoustooptic (AO) devices are based on the inherent nonlinear dependence of the light diffraction efficiency as a function the acoustical wave intensity. In AO devices using a single frequency acoustic wave it is easy to be taken into account to describe all functional properties and limits of the first order diffraction. But in many practical devices using multi-frequency sounds like AO signal processors or multipoint AO deflectors the description are a very complicated, because of a very strong frequency intermodulations. These effects give functional disadvantages in the AO implementations- the decrease of the first order diffraction efficiency maximum to much less than 100%, the appearance of spurious orders and etc. In this work there were developed the theoretical arguments for the possibility to have the appropriate signal dynamic predistortions to have a serious change of mentioned intermodulations and to obtain some advances in limitations of many existing AO devices. The proposal uses the new technique by authors for synthesis and programmable dynamic changes of all RF signals performing the preliminary electronic signal treatment to cancel a certain diffraction modes. The experimental verifications with AO modulators based on TeO2 crystal have been performed. With use of the analogue third order polynomial RF synthesizer there were obtained a good suppression up to 10-15 dB of two-tone second-order intermodulations in area of second order diffraction and two-tone third order spurious modes in the first order diffraction area, in accordance with proper theoretical calculations. There was also verified new technique providing maximal optical power in multi beams laser diagram. In TeO2 AO modulators the growth of the efficiency of two-beam He-Ne laser about 14% was obtained.
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Valery Proklov, Sergey Antonov, Lev Chesnokov, Vyacheslav Chesnokov, Yury Rezvov, "Functional improvements in some of acousto-optic devices by means of preliminary dynamic signal pre-distortions", Proc. SPIE 5953, Acousto-optics and Photoacoustics, 59530L (29 September 2005); doi: 10.1117/12.623748; https://doi.org/10.1117/12.623748
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