Liquid Crystals Under Two Extremes: (1) High-Power Laser Irradiation, and (2) Single-Photon Level

Abstract

This paper describes some of my results on liquid crystal investigations under unconventional, incident light powers: (1) under high-power laser irradiation both in free space and inside laser resonators, and (2) in single-photon source applications for quantum information technology. Several effects under high-power, nanosecond laser irradiation are outlined: athermal helical pitch dilation and unwinding of cholesteric mirrors, showing the limits for using them in laser physics; some pitfalls in measurements of thermal-density refractive nonlinearity and the first observation of thermal lens effects in liquid crystals under several nanosecond, low-pulse-repetition rate (2–10 Hz) laser irradiation in the presence of two-photon absorption; feedback-free kaleidoscope of patterns (hexagons, stripes, etc.) in dye-doped liquid crystals. At the single-photon level, definite linear and circular polarizations of single (antibunched) photons for quantum communications were obtained using single-emitter fluorescence in planar-aligned nematic and cholesteric hosts. Circular polarized cholesteric microcavity resonances were also observed under cw-excitation. In addition, using near-field optical microscopy and AFM, 2D-hexagonal arrays made of cholesteric oligomers were investigated. With progress of this technology, similar arrays can be used for fluorescence control of single emitters.

Keywords:

• Helix unwinding
• liquid crystals
• nonlinear refraction
• single-photon source

Acknowledgments

The author acknowledge the support by the U.S. Army Research Office Award DAAD19-02-1-0285, National Science Foundation Awards ECS-0420888, DUE-0633621, DUE-0920500, and NASA NNX11AM82H Award. Research carried out in Russia was supported by the International Science Foundation Long-Term Award, Russian Government and Russian Foundation for Basic Research Awards.

Some figures were reproduced from Ref. 28 with permission from World Scientific Publishing Co. Pte. Ltd.

The author thanks A.W. Schmid, S.V. Belyaev, V.F. Zolin, Ch.M. Briskina, V.M. Markushev, P. Palffy Muhoray, T. Kosa, B. Taheri, R. W. Boyd and his group members, L.J. Bissell, K. Marshal, L. Novotny and his group members, A. Lieb, J. Winkler, C.R. Stroud, S.-H. Chen and his group members, T. Krauss and his group members for help and/or support. These experiments were carried out in three institutions: the Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Moscow, Russia; the Liquid Crystal Institute (Kent State University), USA; the Institute of Optics, University of Rochester, USA. Some experiments were carried out at the liquid-crystal clean room and nanometrology facilities at the Laboratory for Laser Energetics, University of Rochester. The paper title was suggested jointly with N. Tabiryan.