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Alternate Applications of Liquid Crystals Bobby Geevarughese ECE-E443 Overview Electrically Switchable Bragg Gratings Spatial Light Modulators LCD “Smart” windows Solar Power LC Thermometers 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 LC Gratings http://optics.org/artic les/ole/6/9/7/1/olehol o2%5F87%2D01 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. HPDLC Switchable Bragg Grating 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, SLM http://www.see.ed.ac.uk/research/IMNS/projects/slm/slm.html 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 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/encyclo paedia/hutchinson/m0016763.html “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 “Smart” Windows http://home.howstuffworks.com/smart-window3.htm 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 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 LC Thermometer http://plc.cwru.edu/tutorial/enhanced/files/lc/phase/phase.htm Questions?
