Generating Bessel beams with a tunable acoustic gradient index of refraction lens

Abstract

The Tunable Acoustic Gradient Index of Refraction (TAG) lens is shown to be an alternative method of generating Bessel beam for optical manipulation. The TAG lens exhibits a combination of tunability, optical throughput, and fast switching speed, overcoming many limitations linked with conventional Bessel beam techniques. A refractive fluid is contained within a circular piezoelectric that is driven with an AC signal to establish a periodic index of refraction in the liquid. Simple changes in amplitude or frequency of the driving signal allows for the rapid modification to the transmitted pattern. The switching speed is characterized by the time to reach a steady state pattern, which is shown to depend primarily on the viscosity of the filling liquid. Times between 300 and 2000 μs are obtained corresponding to fluids with viscosity of 640 cs and 0.65 cs respectively.