Spatial Light Modulator

A spatial light modulator (English: Spatial light modulator (SLM) ) is a device for imparting a spatial light modulation. A simple example is the transparency of an overhead projector. In the 80s, large SLMs were placed on overhead projectors to project the contents of computer monitors on a surface ( wall or canvas). There are now SLMs, which are installed within projectors. These are used for example in presentations.

Usually, a SLM modulates the intensity of a light beam, but it is also possible to modulate the phase or the phase and the intensity of the same.

  • 2.1 Pulse shaping
  • 2.2 Holographic Data Storage
  • 2.3 Optical gratings

Modulator types

Electronically addressable SLM ( EASLM )

The pixels in a EASLM be electronically addressed and so generates corresponding images. The communication with the signal generator is done usually use conventional interfaces (eg, a VGA input ). They are commonly used in resolutions up to SXGA (1280 * 1024 ) are available. In contrast to conventional displays, they are much smaller ( of the order of the active region is 2 cm ²). An example of a EASLMs is the Digital Micromirror Device, the (better known as Beamer ) is located in a DLP display.

Optically addressable SLM ( OASLM )

In a OASLM (also optical valve ) a light beam is sent with an impressed pattern on the display, which is simulated by the modulator. Typically, the image information on the display without the presence of light is maintained, but can be optically or electronically removed.

OASLMs are often used as second stage of a high-resolution displays, such as a computer-generated holographic displays. In a process that is called " Active Tiling ", images that are displayed on a EASLM transmitted consecutively on different parts of a OASLMs. Then the image of the OASLMs is shown to the viewer. Since EASLMs can produce up to 2500 frames / s, it is possible to copy about 100 copies of the image of the EASLM 's on OASLM, wherein a liquid running video is still displayed on the OASLM. This will be possible resolutions of up to 100 megapixels.

Applications

Pulse shaping

To form short laser pulses in their temporal structure, one can use an SLM. Here, the pulse is first passed through a dispersive element ( such as a diffraction grating or a prism ) to spatially separate the frequency components. With the help of a spatial phase modulation can now be the individual frequency components of delay time with respect to each other. The allocation to the individual frequency components is reversed by passing the light again on a dispersive element. According to the phase modulation can in principle generate all possible pulse shapes.

Holographic data storage

SLMs are used in the holographic data storage intensely committed to encode information into a laser beam, similar to the way in which this is done by means of an overhead projector transparency. They can also be used as part of a holographic display.

Optical gratings

Similarly, modulators can be used for to make use of the embossed pattern corresponding to a laser beam intensity of optical gratings in which atoms can be trapped and isolated

Optical lattice QinetiQ
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