Alternate Applications of Liquid Crystals

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Alternate Applications of Liquid Crystals

• Bobby Geevarughese
• ECE-E443

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Overview

• Electrically Switchable Bragg Gratings
• Spatial Light Modulators
• LCD
• Smart windows
• Solar Power
• LC Thermometers

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LC Switchable Gratings

• Useful in performing beam steering, beam shaping,
  and other modifications of light intensity or
  phase
• Preferable in WDM
• Bragg phenomenon
• Constructive/destructive interference

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LC Gratings
http//optics.org/articles/ole/6/9/7/1/oleholo25F
872D01
Digilens' gratings are created by using lasers to
polymerize a mixture of monomer and liquid
crystals. An applied AC voltage makes the
material transparent, enabling light to pass
through it.
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HPDLC Switchable Bragg Grating
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Spatial Light Modulators

• Primary use in converting incoherent images to
  coherent
• Potential in correcting defocus, astigmatism, and
  higher order aberrations of human eyes
• Liquid crystal advantages
• Low cost, reliability, compactness, low power
  consumption,

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SLM
http//www.see.ed.ac.uk/research/IMNS/projects/slm
/slm.html
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Liquid Crystal Display

• Nematic phase liquid crystals.
• Nematics consist of a definite order or pattern
• Consists of two sheets of polarizing material
  with a liquid crystal solution between them
• Electric current is passed through the liquid
  crystals (pixels) allowing varying degrees of
  light to pass or not

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LCD

• Segment of seven segment displayed is electrified
• Liquid crystal twists polarized light from front
  filter
• Allows light to bounce off rear reflector and
  illuminate segment

http//www.tiscali.co.uk/reference/encyclopaedia/h
utchinson/m0016763.html
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Smart Windows

• Necessary due to the depletion of available
  energy
• Able to block all light or just some
• With an electrical charge, crystals will align
  parallel to each other and let light through or
  otherwise be scattered
• With liquid crystals there is no intermediate
  setting

http//home.howstuffworks.com/smart-window3.htm
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Smart Windows
http//home.howstuffworks.com/smart-window3.htm
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Solar Cells

• Expensive
• 20-30 cents compared to 6-7 cents

• Organic self assembling thin films
• Contains perylene and HBC-PhC12 which forms
  liquid crystals that when combined leaves
  perylene crystals above HBC film
• Molecule absorbs light, produces an electron, and
  leaves behind a hole
• HBC has disk shaped molecules that stack to
  create molecular wires for hole transport

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LC Thermometers

• Portrays temperatures as colors and can be used
  to monitor changes caused by heat flow
• Various uses from child care to welding
• Contains rod shaped cholesteric liquid crystals
  that form a spiral staircase
• Reflects specific color of light with same
  distance (wavelength) as a full rotation

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LC Thermometer
http//plc.cwru.edu/tutorial/enhanced/files/lc/pha
se/phase.htm
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Questions?