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The photorefractive properties of nominally pure near-stoichiometric LiNbO3 crystals grown from congruent melts containing 11 mol % K2O are studied, and some photorefractive properties which are very different from those in congruent LiNbO3 crystals are observed. Large stationary energy transfer (Γmax=25 cm−1) exists in near-stoichiometric crystals though the photovoltaic field is dominant. The light-induced scattering fanning is markedly asymmetric in the crystals, which is very different from the symmetric fanning observed in congruent ones. Our analysis shows that these differences are caused by the large photovoltaic field and the relatively small density of filled traps in as-grown near-stoichiometric LiNbO3.

Laser‐induced dark traces in doped LiNbO3 crystals are studied with the 1064 nm fundamental radiation and the 532 nm second harmonic radiation of the Nd:YAG laser operating in a pulse mode. The results show that the dark traces are induced only by the 532 nm radiation. The linear relationship between the transmission loss and the 532 nm power density indicates that dark traces are not due to two‐photon absorption. The recovery rates of the absorption in LiNbO3 with different wavelength probe laser are measured and show that laser‐induced dark traces accompany more than one defect appearing in LiNbO3, and disappear quicker at higher temperature.

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.

We show a double phase conjugator with novel crystals of copper-doped potassium sodium strontium barium niobate. The phase conjugation reflectivity can reach 278% and depends on relative input positions of both incident beams. The response time with the input beam power ratio is measured and modeled as a function of input beam power ratio. The formation of the arch coupling loop is analyzed with theoretical simulation results and a positive feedback process is proposed. The influence of a self-pumped phase conjugation process on double phase conjugation fidelity is also discussed. It is necessary to avoid generating self-pumped phase conjugation to prevent the reduction of double phase conjugation fidelity.