Two beam coupling gain enhancements in porphyrin:Zn-doped nematic liquid crystals by using grating translation technique with an applied dc field

The two beam coupling (TBC) gains in porphyrin:Zn-doped nematic liquid crystals (NLCs) are greatly enhanced by adopting the grating translation technique with applying dc electric field. The maximum gain coefficient of Γ=624cm-1, whose value is at least three times larger than that of no grating translation was obtained under the applied dc field of E0=1.2V/μm and the grating translation speed of vq=33.4μm/s. Based on the material and torque balance equations for NLCs taking into account the grating translation, we present the theoretical expressions for TBC gain enhancements, showing excellent agreement with the experimental results.