Incoherent light amplification and phase conjugation of four beams with a photorefractive crystal

A mutually pumped phase conjugator is realized using a bridge configuration with a novel crystal of copper-doped potassium sodium strontium barium niobate. Phase conjugation reflectivity reaches 218%. The buildup times of phase conjugation outputs are measured, and a curve fit of the times is made. A self-curving coupling channel is observed. We use the theory developed by Lyubomudrov and Shkunov to model the coupling channels. The curved beam trajectory depending on the incident position and the incident angle is also calculated. With the results we show that one, two, three, and more four-wave mixing interaction regions exist in photorefractive bridge mutually pumped phase conjugators. Additionally, the simultaneous phase conjugation outputs of four incident beams are also demonstrated experimentally with the crystal.