Growth and Optical Characterization of Cr³⁺:YAB and Cr³⁺:YGAB Crystal for New Tunable and Self-Frequency Doubling Laser

Abstract

We have grown Cr 3+ -doped huntite-borate crystals Cr 3+ :YAB and Cr 3+ :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 cm 2 , 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 Cr 3+ :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 Cr 3+ :YAB crystal with 1.5 times higher conversion efficiency compared with LBO crystal. Consequently Cr 3+ :YAB crystal and Cr 3+ :YGAB crystal have potential as new self-frequency doubling laser materials with tunability.