Abstract

Co²⁺ ions when located in tetrahedral (T_d) sites attract attention due to their intense and wide absorption band related to the ${}^4{\text{A}}_{2_g}\left({}^4\text{F}\right)\to {}^4{\text{T}}_{1_g}\left({}^4\text{F}\right)$ transition. The corresponding saturable absorption is used for the passive Q-switching of erbium (Er) eye-safe lasers at ~1.5 μm. As compared with classical Er phosphate glass with poor thermo-mechanical properties, Er-doped crystals, namely YAG, borates like YAB or YCOB, silicates like CAS, vanadate YVO₄ etc., can provide much better power scaling capabilities [1]. Laser wavelength in this case is shifted up to ~1.7 μm, so state-of-the art saturable absorber (SA), Co:MgAl₂O₄ single crystal cannot be used efficiently.

© 2015 IEEE