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Single crystals of strontium barium niobate (Sr0.61Ba0.39Nb2O6), normally referred to as SBN:61, have been investigated using optical absorption, micro-Raman, photoluminescence, and electron paramagnetic resonance (EPR) techniques. Both undoped and cerium-doped (nominally 0.01 to 0.10% Ce) samples were included in the study. A broad optical absorption band centered near 490 nm and extending to the band edge near 380 nm is observed at room temperature in the Ce-doped crystals. Additional absorption, which we assign to iron, occurs just below the band edge in some of the samples. Photoluminescence data were taken at room temperature. Sharp emission bands at 545 and 650 nm are assigned to Er3+, an emission band at 755 nm is assigned to Ho3+, and a broader emission band extending from 700 to 850 nm is assigned to Cr3+. The SBN:61 crystals strongly absorb 9.4 GHz microwaves. To minimize the effect of these microwave losses, the EPR data were taken near 7 K. A broad isotropic EPR line due to Ce3+ ions is observed at g=0.9 in the Ce-doped samples. Additional isotropic EPR lines due to Fe3+ ions are observed at g=9.35 and g=4.10.

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EPR data confirm the presence of Fe impurities in single-crystal laser hosts of YAlO3. Optical absorption in Fe:YAlO3 was measured to distinguish contributions of Fe3+ and Fe2+ to passive loss in Nd:YAlO3. YAlO3 crystals grown or annealed in H2 contain both Fe2+ and OH− which increase the absorption loss at 1.06 μm and cause fluorescence quenching.