SLM

Spatial light modulator (SLM) is an optoelectronic device that modulates the amplitude, phase, or polarization of light across a two‑dimensional array of pixels. By controlling each pixel, an SLM can reshape a light wavefront, steer beams, or encode information, enabling dynamic holography, beam shaping, and adaptive optics in imaging, display, and laser systems.

The most common SLM technologies are liquid crystal-based devices and digital micromirror devices. Liquid crystal SLMs modulate light by electrically reorienting liquid crystal molecules, yielding either phase-only or amplitude modulation. Reflective liquid crystal on silicon (LCoS) devices are widely used for high-resolution, high-quality phase modulation. Digital micromirror devices consist of an array of tiny mirrors that tilt to produce a binary amplitude modulation, offering high speed and robust operation for certain applications. Other approaches include electro-optic modulators, ferroelectric liquid crystals, and emerging metasurface- or nanophotonic-based modulators, which aim to provide compact, multi‑functional control over light.

Performance characteristics of SLMS include resolution (pixel count and pitch), modulation depth (phase range or amplitude contrast), refresh rate, wavelength coverage, diffraction efficiency, and polarization sensitivity. These factors, along with system alignment and drive electronics, determine suitability for a given task.

Applications span holographic displays and augmented reality, optical trapping and micromanipulation, adaptive optics in astronomy and microscopy, laser processing and materials fabrication, and advanced optical communications. SLM technology continues to evolve with advances in materials, metasurfaces, and multi-wavelength capabilities to expand practical use.