Spatial Light Modulator (SLM) Basics and Vendors

This page covers the basics of Spatial Light Modulators (SLMs) and lists some vendors. It also describes the two main types of SLMs: optically addressed and electrically addressed.

Definition: A Spatial Light Modulator (SLM) is a device that spatially modulates a coherent beam of light.

Types of Spatial Light Modulators (SLM)

There are two main types of spatial light modulators:

• Optically Addressed SLM: Converts incoherent light into a spatially modulated form of light.
• Electrically Addressed SLM: Converts an electrical signal into a spatially modulated form of light.

Figure 1: Operation of an optically addressed Spatial Light Modulator.

The figure above depicts the operation of an optically addressed spatial light modulator. It consists of a photoconductor and a modulator. The photoconductor is typically made using amorphous silicon or a thin film photo transistor. The modulator is often made of liquid crystal.

• Light is detected by the photodetector as a charge distribution.
• This charge distribution affects the modulator, changing the amplitude/phase of the reflected coherent light.
• The liquid crystal changes the polarization of the reflected light based on the electric field.

Drawbacks of Optically Addressed SLMs

Optically addressed SLMs have several drawbacks:

• They are relatively insensitive to light.
• They tend to retain images.
• The liquid crystal degrades over time.
• They offer variable contrast and sensitivity across the device.
• They often have very low yields during manufacturing.

To address these issues, electrically addressed SLMs based on various technologies are used.

Spatial Light Modulator Vendors or Manufacturers

The following are some vendors/manufacturers of spatial light modulators:

• HOLOEYE Photonics AG
• www.jenoptik.com
• Meadowlark Optics, Inc.
• Texas Instruments
• Laser 2000, UK