Photorefractive properties of co-doped potassium sodium strontium barium niobate crystals

The transmissivity and the results of two-beam coupling and self-pumped phase conjugation (SPPC) experiments on Co-doped potassium sodium strontium barium niobate (KNSBN) single crystals are reported. The Co ions doped into KNSBN can form a deep energy level near 2.25 eV. The two-beam coupling gain coefficients of the Co-doped KNSBN are nearly 20 cm(-1) at 2 theta = 37 degrees for the transmission photorefractive index grating and larger than 29.2 cm(-1) for the reflecting photorefractive index grating. A striking single-beam asymmetric transmission was observed. The maximum SPPC reflectivity is larger than 70% at theta = 49.7 degrees for an intensity W = 77 mW, which is the largest value measured in the family of KNSBN crystals.