Paper detail

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

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.