Photoinduced short-lived absorption in GSGG:Cr3+:Nd3+ and GSAG:Cr3+:Nd3+ crystals

An investigation was made of the influence of short-wavelength pump radiation on the spectral and luminescence characteristics of GSGG:Cr³⁺:Nd³⁺ and GSAG:Cr³⁺:Nd³⁺ crystals. A sensitive system was developed for measurement of the induced absorption based on multipass probing of a crystal by laser radiation. Dependences of the induced absorption on the excitation energy and the lifetimes of the photoinduced color centers were determined and the influence of the induced absorption on the pumping efficiency of the laser active element was studied. It was established that the intensity of the photoinduced absorption in a GSAG:Cr³⁺:Nd³⁺ crystal was substantially lower than that in a GSGG:Cr³⁺:Nd³⁺ crystal. It was shown that the induced absorption reduces the efficiency of filling of the ⁴F_3/2 upper active level of the Nd³⁺ ion.