Nonlinear Optical Features of Cr ⁴⁺ : YAG Transparent Ceramics for all Solid‐State Laser

Chromium‐doped yttrium aluminum garnet (Cr 4+ : YAG) transparent ceramics (TCs) have significant applications in 1 µm passively Q‐switched (PQS) lasers. The issues of low conversion rate of Cr 4+ ions and the impact of different Cr doping concentrations on the PQS lasers are key problems that need to be resolved. In this paper, the energy band structures and optical absorption spectra of Cr: YAG were calculated by first principles. The different doping concentrations of Cr 4+ : YAG TCs were fabricated by the solid‐state reaction, and their output properties of PQS lasers were investigated. It is surprising that the pulse energy reached 0.52 µJ for 0.1 at.% Cr 4+ :YAG TC, which was a 3‐fold increase from that of the 0.05 at.% Cr 4+ :YAG TC (0.15 µJ). Besides, the peak power of 0.1 at.% Cr 4+ :YAG TC was 1.25 W, which was about 5 times higher than that of the 0.05 at.% Cr 4+ :YAG TC (0.26 W). Furthermore, the pulse width of the 0.1 at.% Cr 4+ :YAG TC was 417 ns, which was smaller than that of the corresponding 0.05 at.% Cr 4+ :YAG TC. These results show that the Cr 4+ : YAG TC with superior nonlinear absorption, offering a valuable reference for future research on the nonlinear optical properties of Cr 4+ : YAG TC.