Abstract

In most photorefractive materials with a large diffusion-type non-linearity, it is often observed that light beams follow curved paths [1], [2]. This phenomenon is known as the self-bending effect. We propose a two-wave mixing (2WM) interaction in BaTiO₃ between such a self-bended pump beam and a weak signal beam that permits to achieve very high-gain 2WM. In our new 2WM configuration (Fig. 1), the extraordinary-polarized pump beam P_in, incident on the (010) face of the crystal, rapidly undergoes a bended trajectory in the direction of the c-axis. The output self-bended pump beam $P_{\text{out}}^{\prime }$ then emerges from the (001) face perpendicularly to the entrance face. The input signal beam S_in, incident on the (001) face, is arranged to interact with the bended beam. In the steady state, the intensity into $P_{\text{out}}^{\prime }$ represents about 45 % of the total output intensity. Thus, an interesting feature of such configuration is that an important amount of the incident pump energy is guided into the self-bended beam. More energy is thus available for the 2WM coupling while in a conventional 2WM geometry where the pump and the signal beams enter the crystal at the same (001) face [3],[4], the pump beam P_out is almost completly depleted (~ 95 %) into the fanning, corrupting the 2WM gain.

© 1995 Optical Society of America