High gain of light in photoconducting polymer-nematic liquid crystal hybrid structures

A liquid crystal panel useful for a realtime holography exhibiting also very high exponential gain coefficient is presented. We prepared nematic liquid crystal layer sandwiched between photoconducting polymeric layers (poly(N-vinylcarbazole)/trinitrofluorene). The first-order diffraction efficiency measured in degenerate two-wave mixing experiment amounts to 44%. The most important feature of the presented panel is its ability to switch energy from beam to beam. In two-wave coupling experiment multiple orders of diffraction are present and a very high two-beam coupling gain ratio (12) and a net exponential gain coefficient Gamma = 3700 cm(-1) have been measured. This gain was achieved in samples biased by a de external electric field and tilted with respect to the beam incidence bisector at 15 degrees. The time constants of grating formation and erasing in the studied system are functions of applied voltage and can be made as short as few milliseconds at favorable conditions. (C) 2001 Elsevier Science B.V. All rights reserved.