Electrically switchable random to photonic band-edge laser emission in chiral nematic liquid crystals

• Published in: Applied physics letters Vol. 100; no. 7; pp. 071110 - 071110-3
• Main Authors: Morris, Stephen M., Gardiner, Damian J., Hands, Philip J. W., Qasim, Malik M., Wilkinson, Timothy D., White, Ian H., Coles, Harry J.
• Format: Journal Article
• Language: English
• Published: American Institute of Physics 13-02-2012
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.3684804

Using a chiral nematic liquid crystal with a negative dielectric anisotropy, it is possible to switch between band-edge laser emission and random laser emission with an electric field. At low frequencies (<1 kHz), random laser emission is observed as a result of scattering due to electro-hydrodynamic instabilities. However, band-edge laser emission is found to occur at higher frequencies (>5 kHz), where the helix is stabilized due to dielectric coupling. These results demonstrate a method by which the linewidth of the laser source can be readily controlled externally (from 4nm to 0.5nm) using electric fields.