Quasi-in-Plane Leaky Lasing Modes from Thin Waveguiding Layers of Nematic and Cholesteric Liquid Crystals

Abstract

Lasing from dye doped liquid crystals was observed in the nematic, cholesteric and isotropic phases of liquid crystals in the plane waveguide geometry without mirrors and special modulation of the gain or refraction index by a holographic or other technique. The light was generated in a liquid crystal layer confined by two glasses with or without semitransparent electrodes, which formed an optical waveguide. A strong light amplification occurred along the narrow stripe produced by the pump beam with the necessary feedback provided by the walls of the waveguide. The lasing modes leaked into the glasses, were guided therein at very grazing angles and left the cell from its edges. The intensity and polarization of the lasing light depend on refraction indices of the liquid crystal and confining glasses. The conditions for lasing were discussed both analytically and numerically on the simplest example of the dye doped isotropic phase.

Keywords:

• dye lasers
• liquid crystals
• waveguides

Acknowledgments

The authors thank Prof. E. A. Luk'yanets and Dr. V.I. Alekseeva for supplying Chromene laser dye and Mr. A. Pane (LiCryL-CNR) for the help in experiment. The Russian group was supported by RFBR (grants no. 04-02-16466 and 05-02-16703) and Russian Federal Project (project 02.434.11.2025). The Italian group acknowledges the support from CNR-INFM and the CEMIF.CAL funds.