Spatial Light Modulator(SLM) basics and Vendors

This page covers basics of Spatial Light Modulator(SLM). It mentions vendors of Spatial Light Modulators. It also describes types of SLM(spatial light modulator) viz. optically addressed and electrically addressed.

Definition: The device which spatially modulates coherent beam of light is known as Spatial Light Modulator.

Types of Spatial Light Modulator(SLM)

There are two types of spatial light modulators as mentioned below.
• Optically addressed SLM: It converts incoherent light into spatial modulation form of light.
• Electrically addressed SLM: It converts electrical signal to spatial modulation form of light.

SLM-Spatial Light Modulator

The figure-1 depicts operation of spatial light modulator of optically addressed type. It consists of photo conductor and modulator. Photo conductor is made using amorphous silicon or thin film photo transistor. Modulator is made of liquid crystal.
• Light is detected by photo-detector as charge distribution.
• This will affect the modulator and hence will change the amplitude/phase of reflected coherent light. Liquid crystal changes polarisation of reflected light based on electric field.

Following are the drawbacks of optically addressed SLM:
• It is relatively insensitive to the light.
• It tends to retain image.
• Liquid crystal degrades over time.
• It offers variable contrast and sensitivity across the device.
• It offers very low yield during manufacturing.

To address these issues, Spatial Light Modulators such as electrically addressed SLM based on various technologies is used.

Spatial Light Modulator Vendors or Manufacturers

Following are the vendors/manufacturers of spatial light modulator.
• HOLOEYE Photonics AG
• Meadowlark Optics, Inc.
• Texas Instruments
• Laser 2000, UK

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