Near-infrared wavelength-dependent nonlinear transmittance tailoring in glass ceramics containing Er3+:LaF3 nanocrystals

Nonlinear optical (NLO) effects originating from materials doped with rare-earth ions possess colossal potential for application in all-optical switches. However, among previous studies, Er3+ ion-doped glass ceramics (GCs) with remarkable NLO features have been investigated with respect to optical modulation applications by tailoring their nonlinear transmittance upon excitation at various near-infrared (NIR) wavelengths, which might prove to be a simple way of achieving "on-off" optical modulation in future all-optical switches. Here, we present the first observation of tailorable nonlinear transmittance in germanate oxyfluoride GCs containing Er3+: LaF3 nanocrystals, manipulated by excitation at 808, 980, and 1550 nm, which is consistent with the results from theoretical calculations and simulations. Furthermore, we conduct experimental investigation and analysis related to energy level transitions and dynamical evolution, indicating that these intriguing NLO features can be attributed to the differentiation between excited state absorption accompanied by up-conversion luminescence and stimulated emission processes during excitation at discrepant NIR wavelengths. Importantly, bidirectional optical switching for the "on-off" toggle effect has been successfully demonstrated by selectively tailoring the nonlinear transmittance of the single Er3+-doped GCs. This tailorable NLO behavior of Er3+-doped GCs, which is dependent on excitation at different NIR wavelengths, might provide a versatile strategy for the development of next-generation bidirectional all-optical switches.