Cholesteric liquid crystal laser with wide tuning capability

This letter examines a planar cholesteric cell (CLC) doped with two collocated laser dyes as a one-dimensional photonic crystal. Adding phototunable chiral material (AzoB) allows the CLC photonic crystal to be lased at the band edges of the photonic band gap with a tuning range of over 100 nm. Tuning is performed by irradiating the chiral AzoB material with UV light, causing the material to undergo trans-cis isomerization in the CLC film. The tuning range is the visible region from 563 to 667 nm. Moreover, the tuning is reversible. (c) 2005 American Institute of Physics.