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?