Growth and optical characterization of Cr3+:YAB and Cr3+:YGAB crystal for new tunable and self-frequency doubling laser

We have grown Cr3+-doped huntite-borate crystals Cr3+:YAB and Cr3+:YGAB by the top-seeded solution growth (TSSG) method. These crystals have a broad fluorescence ranging from the red to near-IR spectral region, and their lifetimes were measured as 170 μs and 87 μs, respectively. The emission cross sections are estimated to be 0.8×10-20 and 1.6×10-20 cm2, respectively. The vibronic levels of their ground state were estimated to be 1400 cm-1, so they can provide a four-level system. The optical gain of Cr3+:YAB crystal was measured in the range from 744 nm to 852.5 nm. The maximum single-pass gain was 1.9 at 830 nm. Second harmonic generation in the UV region (375 nm) was obtained by a Cr3+:YAB crystal with 1.5 times higher conversion efficiency compared with LBO crystal. Consequently Cr3+:YAB crystal and Cr3+:YGAB crystal have potential as new self-frequency doubling laser materials with tunability.