Noise Reduction in Photorefractive Image Amplification by Contradirectional Two-Wave Mixing in Rh-Doped BaTiO₃ Crystal

Low noise image amplification owing to contradirectional two-wave mixing (CTWM) is proposed and demonstrated in Rh-doped BaTiO₃ crystal. Comparing with the conventional forward two-wave mixing scheme, an enhancement of signal-to-noise ratio in the order of 10³ is obtained. The theoretical analyses are presented and give a reasonable explanation for the experimental results. The further discussion shows that CTWM scheme can also reduce the influence of the crystal absorption and crystal size on the two-wave mixing process to rise the signal beam gain.