A Spatial Light Modulator (SLM) is an optical device that can dynamically modify the spatial properties of a light beam. Unlike fixed optical elements such as lenses or gratings, an SLM consists of a two-dimensional array of individually addressable pixels. Liquid crystals are birefringent, so applying a voltage to the cell changes the effective refractive index seen by the incident wave, and thus the phase retardation of the reflected wave. It plays a crucial role in fields like holography, microscopy, and even augmented reality, where managing light behavior is key. The Fourier transform of the input beam is multiplied by a stored Fourier transform in the Fourier plane.