Spatial light modulator

[2] SLMs are used extensively in holographic data storage setups to encode information into a laser beam similarly to the way a transparency does for an overhead projector.

In the 1980s, large SLMs were placed on overhead projectors to project computer monitor contents to the screen.

Unlike ordinary displays, they are usually much smaller (having an active area of about 2 cm²) as they are not normally meant to be viewed directly.

Phase modulation can be achieved using a DMD by using Lee holography techniques, or by using the superpixel method.

A photosensor allows the OASLM to sense the brightness of each pixel and replicate the image using liquid crystals.

This technique features with full calibration and control of the ultrashort pulse, with no moving parts, and simple optical setup.

Linear array SLMs that use nematic liquid crystal elements are available that can modulate amplitude, phase, or both simultaneously.

Schematic of a liquid crystal-based Spatial Light Modulator. 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.