RESONANTLY INDUCED REFRACTIVE-INDEX CHANGES IN EU-3+-DOPED AND ER-3+-DOPED SILICATE AND PHOSPHATE-GLASSES

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 I-4(11/2) 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 (almost-equal-to 1000 cm-1) phonon-induced structural transition.