Cover story: Yang YQ, Forbes A, Cao LC. A review of liquid crystal spatial light modulators: devices and applications. Opto-Electron Sci 2, 230026(2023).

Light has been harnessed for centuries for various applications, which started with simple refractive and reflective solutions such as lenses and mirrors. The rise of the micro-electronics and electronic computing saw novel optical designs emerge a few decades ago based on diffraction and interference, but the field did not gain much traction due to the complexity of implementation, namely the expensive and hard to manufacture hard-coded optics. This changed only recently with the ability to realize on-demand light tailoring with a novel digital toolkit based on liquid crystal spatial light modulators, a technology originally aiming for illumination. In this review, the authors show how this modern digital toolkit has surpassed the performance of traditional approaches on controlling light, and fueled new applications that would have been impossible before. They include novel forms of structured light, control of single photons and entangled states, real-time light control in metrology, optical trapping and tweezing, and optical communication. Consequently, the technology has proven to be fast, cheap, versatile and robust, and therefore ubiquitous over the world today. The authors unpack the physics of liquid crystal SLMs in the context of modern applications and the nascent field of structured light, offering a holistic introduction to the topic from fundamentals to applications.