Optical amplification in nematics doped with carbon nanotubes

We present results on the orientational photorefractive effect in a mesogenic nematic doped with multiwalled carbon nanotubes. Efficient coherent-beam amplification of a signal beam by energy exchange with a pump beam was observed in homogeneous cells of the doped liquid crystal E7 at electric fields of similar to0.5 V/mum. Photorefractive gains as high as 10(3) cm(-1) are achieved in the Raman-Nath regime. It is found that the gain coefficient depends strongly on the externally applied dc voltage, the pump/probe intensity ratio and the total input intensity. (C) 2001 American Institute of Physics.