Two-beam coupling has been studied at red and near-infrared wavelengths in blue Rh:BaTiO(3). High amplification, of the order of 20,000-37,000, of a weak signal beam has been measured. The effect of strong intensity-dependent transmission is considered when theoretical plots are fitted to the experimental data.
Low noise image amplification owing to contradirectional two-wave mixing (CTWM) is proposed and demonstrated in Rh-doped BaTiO 3 crystal. Comparing with the conventional forward two-wave mixing scheme, an enhancement of signal-to-noise ratio in the order of 10 3 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.
The buildup and the decay of photorefractive two-beam coupling are experimentally demonstrated to be strongly dependent on the intensity ratio of the two beams (signal-to-pump ratio). The experiment, done with a BaTiO3 crystal, shows good agreement with the theory of two-beam coupling in the depleted-pump regime. The deviation of the response behavior from the small-signal regime is seen for ratios as small as ∼10−5. These results are significant for applications of two-beam coupling as gain media, especially for the elimination of amplified noise (fanning).