Parameter estimation of an acousto-optic focusing device for visible radiation

Subject of study . An acousto-optic (AO) focusing device using linearly frequency-modulated ultrasonic waves is studied. Aim of study. The parameters of the AO focusing device are determined to estimate the aberrations introduced by it. Method. AO interactions in the low-diffraction-efficiency regime are modeled numerically. Main results. A model that accounts for the length of the AO interaction and the diffraction effects is developed. The results show that the focal spot is a narrow strip with a strongly asymmetric structure, and the wavefront within the spot is tilted by approximately 4° relative to the wavefront of the incident beam. In the case of oblique incidence of radiation on the focusing device, the spot size reduces by a factor of approximately 2; that is, it reduces to 17 µm at the 84% level of the energy concentration function. Further, the focal spot structure becomes symmetric. Practical significance. The obtained results can be used in the development of adaptive optical systems.