Acousto-optic holography for micrometer-scale grid patterning of amplified laser pulses with single-pulse accuracy

TL;DR

This paper demonstrates a method for micrometer-scale 2D grid patterning of amplified laser pulses using acousto-optic holography with single-pulse accuracy, enabling fast, precise light shaping.

Contribution

It introduces a pseudo 2D acousto-optic holography technique with algorithms for phase and amplitude modulation, achieving single-pulse pattern switching.

Findings

Achieved micrometer-scale 2D point grid patterning.

Suppressed side lobes with amplitude modulation.

Enabled pattern switching between individual laser pulses.

Abstract

Many optical systems use acousto-optics for fast steering of light. However, acousto-optic (AO) light diffraction permits manipulation and shaping of light fields in a much broader sense including holography. While acousto-optic devices operate at incontestable speed, they are one dimensional (1D) diffraction devices depending on analog serial data transfer and as such have a mode of use distinguished from common 2D spatial light modulators. Combination with an amplified laser source allows to clock the serial buildup of AO diffraction patterns for avoidance of phase aberration in the output beam due to acoustic wave progression. Pseudo 2D holography is established with two crossed AO deflectors for biaxial spatial modulation of the input phase, and optionally also of its amplitude. In this configuration, acousto-optics permits light patterning into micrometer-scale 2D point grids with the possibility to switch the pattern between individual laser pulses. We describe algorithms for deriving AO holograms for either pure phase modulation or for a co-modulation of amplitude. Computationally reconstructed phase holograms show focal patterns in presence of side lobes. Side lobes are entirely suppressed by amplitude modulation, though at the expense of reduced optical power transmission.