Kent State
University chemical physics graduate student Andrii Varanytsia demonstrates laser
emission with a liquid crystal elastomer in Professor Peter
Palffy-Muhoray’s lab at the
Liquid Crystal and
Materials Sciences Building on the university’s Kent Campus.
(December 22, 2015) Liquid
crystal elastomers (LCEs), essentially rubbers with liquid crystal properties,
can do a number of fascinating things, especially in the fields of optics,
photonics, telecommunications and medicine. They can curl up, bend, twist,
wrinkle and stretch when exposed to light, heat, gases and other stimuli.
Because they are so responsive, they are ideal for applications like artificial
muscles and blood vessels, actuators, sensors, plastic motors and drug delivery
systems. They can even be used as a mechanically tunable mirrorless “rubber”
laser.
In the College of Arts and Sciences at Kent State
University, Peter Palffy-Muhoray, Ph.D., associate director of the Glenn H. Brown
Liquid Crystal Institute® and professor of chemical physics, has been
collaborating with the world’s experts in liquid crystal elastomers research
for many years. Recently, he and his graduate assistant, Andrii Varanytsia, and
Kenji Urayama and Hama Nagai from the Kyoto Institute of Technology in Japan
developed the first type of cholesteric liquid crystal elastomers with special
properties that enable it to precisely emit laser light, without the use of
mirrors, while being stretched.
Lasers consist of cavities, typically formed by fixed
mirrors. Light bouncing between these has a characteristic frequency, just like
a guitar string of a certain length. Light-emitting material in the cavity
amplifies the light wave, which is then emitted at a precise frequency – like a
pure tone from some musical instrument.
A liquid crystal
elastomer is used as a mechanically tunable mirrorless “rubber” laser in the lab of
Peter Palffy-Muhoray, Ph.D., associate director of the Glenn H. Brown
Liquid Crystal Institute and
professor of chemical physics at Kent State
University. The elastomer has properties that enable it to
precisely emit laser light,
without the use of mirrors, while being stretched.
In 2001, Palffy-Muhoray, Bahman Taheri, Ph.D., and several
other colleagues were the first to demonstrate that they could use liquid
crystals to bounce laser light back and forth inside the material, without the
need for any external mirrors. However, accurate control of the laser emission
frequency was not possible then.
Their recent work, funded by the U.S. National Science
Foundation and Japan Society of Promotion of Science, was published on Nature.com
on Dec. 4 in an article titled “Tunable Lasing in Cholesteric Liquid Crystal
Elastomers With Accurate Measurement of Strain.”