Nematic liquid crystal optical amplifier consisting of layered structures

Coherent amplification was observed in an optical structure with multilayer C₆₀ doped nematic films, in which photorefractive gratings working in the Raman-Nath regime were created, leading to an asymmetric energy transfer in two-beam coupling. This multilayer optical structure exhibited exponential dependence of the signal gain on the number of nematic layers when higher-order diffractions were negligibly small. A gain of the 0.1 signal as high as ∼4000 was achieved in the six-layer sample at a low dc voltage of 1.2 V and a low pump beam power of 8 mW. The gain of this ultrahigh sensitive six-layer sample depended strongly on the pump to signal beam power ratio as well as the power of the signal.