Resonantly induced refractive index changes in Eu3+- and Er3- doped silicate and phosphate glasses

Abstract

Light-induced refractive index gratings were investigated in Eu3+- and Er3- -doped silicate and metaphosphate glasses using four wave mixing (FWM) at 300 K. Transient and permanent gratings were observed in the Eu3+ -doped glasses upon resonant excitation of the non-radiative 5D2 state, whereas excitation of the non-radiative 4I112 level of Er3+ yielded no grating formation. The latter was confirmed with a single beam lensing experiment in the Er3+ -silicate glass, which showed only transient thermal refractive index changes. The Er3+ results are inconsistent with a previously developed two-level system model, which ascribes the permanent grating formation in the Eu3+ glasses to a high energy (≃ 1000 cm−1) phonon-induced structural transition.