Acousto-optic deflectors applied as high performance spatial light modulators

2019 edition

Dorian Treptow

Spatial light modulators are a key tool for modern applications and research in the field of optics. A variety of light modulator technologies exist that serve for different applications according to their properties. Acousto-optic deflectors (AODs) are light modulating devices that have a wide range of applications because of their immense speed and accuracy. Their main functionality is the deflection of a laser beam. And the deflection angle is controlled by the frequency of an electrical driving signal. By generating complex modulated driving signals with modern signal generators, it is possible to enhance the functionalities of AODs what improves their performance drastically and enables new applications.
We develop advanced signals by combining the acousto-optic modulation with superimposed optical diffraction gratings. These gratings are calculated computationally by simulating the backwards propagation of a laser beam that passes an AOD. A simple relationship between the driving signal and the acousto-optic modulation allows to display these gratings on the AODs by encoding the characteristics of the grating in the driving signal.
By driving two crossed AODs with our advanced signals, we formed a single laser beam into two-dimensional separable laser patterns at a kilohertz range. The reconstruction speed of the separable patterns, that consist of more than 200.000 individual laser spots, was a thousand times faster compared to conventional deflection signals. With a sophisticated sequencing of signals, we also projected arbitrary laser patterns in real-time with astonishing quality by reducing typical laser speckle.
The obtained results suggest new applications e.g. in laser projection, laser material processing, microscopy and optical micromanipulation.