Twisted crystals

University of Rochester researchers have patented a new class of optical materials that efficiently create ‘pure polarized light,’ which uses far less energy than conventional LCD technology to produce the same images.

University of Rochester researchers have patented a new class of optical materials that efficiently create “pure polarized light,” which uses far less energy than conventional LCD technology to produce the same images.

The technology, called glassy liquid crystals, has been licensed to Cornerstone Research Group, of Dayton, OH for manufacture and use in displays, optical drives, and “colour tuneable” filters.

The material the team has developed is based on liquid crystal technology but is very different from traditional materials. Conventional liquid crystals flow at room temperature, and the rod-like molecules stand at attention when an electric field is applied, giving manufacturers a way to control how light moves through them.

In contrast, the new materials are solid, stable films that are as clear as glass but whose molecules are also highly ordered, unlike normal glass.

“This is really liquid crystal glass, because it has characteristics of both glass and liquid crystals,” says Chen, professor of chemical engineering and materials science and senior scientist at the Laboratory for Laser Energetics (LLE) at the University of Rochester.

The materials are actually stacks of layered molecules, each rotated slightly so that together the molecules form a clear spiral path for light to follow. Altogether the layers, which form themselves spontaneously into this rotational pattern, are anywhere from 4 to 35 microns thick, less than half the thickness of a human hair. When hit with unpolarized light from an ultraviolet source, the materials emit circularly polarized, colour light. Residual light is reflected and recycled, rather than absorbed and wasted as in current systems.

Most displays today use linear polarization, even though it’s not as efficient as circular polarization, and then use additional optical devices to produce colour. “Up to now there simply haven’t been materials to pursue this avenue of research,” Chen says. “We’re hoping to make circular polarization an option for display technology.”

Besides brighter and more efficient displays, other applications of glassy liquid crystals include laser goggles that selectively filter out laser light at certain wavelengths, and electro-optic devices for optical communication. Chen says the materials also have potential for optical storage, since at high temperatures they can switch states instantly in response to heat or light.

Samples of the glassy liquid crystals can be purchased from Cornerstone Research for experimental use and product development by calling 937-458-0210.