Liquid crystal tunes fiber

Researchers from the Technical University of Denmark, Chalmers University of Technology in Sweden and Crystal Fibre A/S in Denmark have combined photonic crystal and liquid crystal to make an optical fiber whose properties can change according to temperature.

The combination allows the researchers to change the properties of the light inside the fiber. Ordinarily, switching, filtering and altering the polarization of light requires moving the light from the fiber to an external device, then returning it to the fiber.

The material could lead to cheaper and faster control of the optical signals used in telecommunications lines.

Photonic crystals are made from microscopic rods or a solid containing patterns of holes. The rod or hole patterns prevent certain wavelengths of light from passing through. Liquid crystal is made up of molecules that can be aligned, but only in one direction, resulting in a material somewhere between a liquid and a solid.

The researchers made a thermal-optic fiber switch by filling the holes of a section of photonic crystal fiber with liquid crystal. Changing the temperature of that section alters the liquid crystal, which changes the optical properties of the fiber.

The photonic crystal/liquid crystal optical fiber could be used in practical applications in 2 to 5 years, according to the researchers. The work appeared in the October 6, 2003 issue of Optics Express.