Laser-induced refractive-index gratings in Eu-doped glasses

Four-wave-mixing techniques were used to establish and probe refractive-index gratings in Eu³⁺-doped silicate and phosphate glasses. When the Eu³⁺ ions are resonantly excited, superimposed transient and permanent gratings are formed. The former are characteristic of population gratings of excited Eu³⁺ ions while the latter are attributed to local structural modifications of the glass hosts. The time dependences of the grating buildup, decay, and erasure are reported as a function of temperature, laser power, and ``write''-beam crossing angle for each of the samples. The results suggest the use of laser-induced gratings in these glasses in applications such as amplitude-modulated phase-conjugate reflectors.