Extending Spatial Light Modulation into the Ultraviolet
Researchers routinely marshal hundreds of cold atoms into individual traps using arrays of tightly focused laser beams known as optical tweezers. Thanks to an additional device called a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM), any and all of the atoms can be moved back and forth in less than a millisecond. Unfortunately, LCOS-SLMs work only at infrared and visible wavelengths. Applications that take advantage of ultraviolet (UV) light’s shorter wavelengths and higher energies are off limits because UV damages the liquid crystals’ organic molecules. Now Johannes Zeiher of the Ludwig Maximilian University of Munich and colleagues have demonstrated an SLM that works in the UV range [1].
Like an LCOS-SLM, the new UV modulator alters the phase of incident radiation and creates patches of high and low intensity via interference. Unlike an LCOS-SLM, which works by refraction, the UV modulator works by reflection. The main component is an array of 256 × 256, 16-µm-wide aluminum mirrors. Each mirror’s height is controlled by an electrically activated piston. When uniform UV laser light strikes the array, the mirrors confer on the reflected light an intricate and adjustable pattern.
The Fraunhofer Institute for Photonic Microsystems in Germany had already developed the modulator for a range of applications. To prove that it could work with optical tweezers, Zeiher and his colleagues had to correct aberrations introduced by the mirrors, show that the pistons did not introduce excessive noise, and demonstrate that the individual beam from each mirror has a desirable flat profile. Now that the researchers have tested the device, they plan to use it in experiments relevant to quantum computing with neutral atoms and to quantum simulations of large, 2D quantum magnets.
–Charles Day
Charles Day is a Senior Editor for Physics Magazine.
References
- M. Ammenwerth et al., “Dynamical spatial light modulation in the ultraviolet spectral range,” Phys. Rev. Appl. 24, 034031 (2025).