Abstract
Holographic light modulation is the most efficient method to shape laser light into well-defined patterns and is therefore the means of choice for many intensity demanding applications. During the last two decades, spatial light modulators based on liquid crystals prevailed among several technologies and became the standard tool to shape light holographically. But in the near future, this status might be challenged by acousto-optic deflectors. These devices are well known for their excelling modulation rates and high optical power resilience. But only few scattered precedents exist that demonstrate their holographic capabilities, despite the many interesting properties that they provide. We implemented a holographic acousto-optic light modulation (HALM) system, that is based on displaying holograms on acousto-optic deflectors. We found that this system can eliminate the ubiquitous coherent artifacts that arise in holography through the inherent motion of acousto-optic holograms. That distinguishes our approach from any other holographic modulation technique and allows to reconstruct intensity patterns of the highest fidelity. A mathematical description of this effect is presented and experimentally confirmed by reconstructing images holographically with unprecedented quality. Our results suggest that HALM promotes acousto-optic deflectors from highly specialized devices to full-fledged spatial light modulators, that can compete in a multitude of applications with LC-SLMs. Especially applications that require large optical output powers, high modulation speeds or accurate gray-scale intensity patterns will profit from this technology. We foresee that HALM may play a major role in future laser projectors and displays, structured illumination microscopy, laser material processing and optical trapping.
Highlights
Holographic light modulation is the most efficient method to shape laser light into well-defined patterns and is the means of choice for many intensity demanding applications
Acousto-optic holograms are displayed on an acousto-optic deflector (AOD) by encoding a computer-generated hologram (CGH) Gk into the electrical driving signal
We demonstrated theoretically and experimentally that the motion of holograms, displayed on an acousto-optic deflector, inherently eliminates coherent artifacts in holographically reconstructed laser patterns
Summary
Holographic light modulation is the most efficient method to shape laser light into well-defined patterns and is the means of choice for many intensity demanding applications. Impairs the resolution and contrast of a holographically reconstructed pattern, because phase holograms form images through interference and rely on a high degree of light coherence Another class of methods is based on generating uncorrelated holographic speckle patterns successively over time, which average out when integrated by a detector. That allows an extremely fast beam scanning at kilohertz rates, which found many applications in material processing, microscopy and optical m icromanipulation[15,16,17,18,19] It has been demonstrated in few precedents, which are scattered over decades and various fields of optics and photonics, that complexly modulated signals allow AODs to change the shape of a laser beam or to generate multi-spot patterns[20,21,22,23,24] (see Fig. 1c)
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