Coherent amplification was observed in an optical structure with multilayer ${\mathrm{C}}_{60}$ 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 $0.1\mathrm{\mu W}$ signal as high as $\sim 4000$ was achieved in the six-layer sample at a low dc voltage of $1.2\mathrm{V}$ and a low pump beam power of $8\mathrm{mW}$ . 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.