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Description
Some applications of quasi-collinear acousto-optic (AO) cells, such as laser pulse generation and shaping, microscopy, spectroscopy, and multicoloured optical tweezers, require the creation of precisely defined distribution of the acoustic field frequency and amplitude along the entire AO interaction length. If the actual acoustic field structure inside the AO crystal deviates from the desired one, the spectral components of the input optical pulse are diffracted in the areas with improper characteristics. It leads to a distortion of the diffracted beam spectral profile at the output. Numerical modeling is sometimes insufficient, since the AO cells geometry may differ due to an inaccurate fabrication, which significantly modifies the acoustic beam structure along the AO interaction length. In this work, an acoustic field visualization technique for the quasi-collinear geometry of AO interaction is demonstrated as an effective tool for analyzing the redistribution of acoustic power caused by acoustic anisotropy, acoustic power absorption and temperature gradients. We experimentally obtained high-contrast 3D maps of the acoustic power distribution in a quasi-collinear AO cell based on a tellurium dioxide crystal. The proposed approach provides a more consistent and reliable way to characterize the acoustic field structure.