Removing the discontinuous shifts in emission wavelength of a chiral nematic liquid crystal laser

The laser wavelength of a band-edge liquid crystal laser is known to vary in a stepwise fashion with temperature. This report describes a method for removing the discontinuous shifts in the laser wavelength by doping a nematic sample with two different chiral dopants which exhibit opposing dependences of the natural pitch on temperature. On cooling from the isotropic phase to room temperature the total shift of the laser wavelength is 15 nm with no discontinuities. This is in contrast to that observed for samples consisting of only one chiral dopant whereby the wavelength shift was as large as 75 nm for the same temperature range.