Nonlinear optical (NLO) effects rooting from rare-earth ions doped materials possess colossal potential application in all-optical switches. However, among previous researches, Er 3+ ions doped glass ceramics (GCs) with remarkable NLO features has been overlooked for optical modulation application by tailoring its nonlinear transmittance upon excitation of various near-infrared (NIR) wavelengths, which might give effortless way of achieving "on-off" optical modulation in future all-optical switches. Here, we present the first observation of the tailorable nonlinear transmittance performances in germanate oxyfluoride GCs containing Er 3+ :LaF 3 nanocrystals as manipulated by excitation of 808, 980, and 1550 nm, respectively; which is in good correspondence to the results from theoretical calculations and simulations. Furthermore, we conduct experimental investigation and analysis by relying on energy level transitions and dynamical evolution, suggesting that this intriguing NLO features is attributed to the differentiation between excited state absorption accompanied by up-conversion luminescence and stimulated emission processes during excitation of discrepant NIR wavelengths. Importantly, the bidirectional optical switching for "on-off" toggle effect has been successfully demonstrated by selectively tailoring the nonlinear transmittance of the single Er 3+ -doped GCs. This tailorable NLO behaviors of Er 3+ -doped GCs dependent on excitation of different NIR wavelengths might provide a versatile strategy for the development of next-generation bidirectional all-optical switches.ions doped GCs, 21 which is beneficial to generate much more remarkable NLO features and prompts us to study it.Nevertheless, a method for the realization of optical modulation in a single Er 3+ -doped GCs with a fixed composition based on excitation of various NIR wavelengths has been overlooked for the development of future all-optical switches. 22, 23 Therefore, it might be much meaningful to investigate the NIR wavelength-dependent nonlinear transmittance of Er 3+ -doped GCs (Here, germanate oxyfluoride GCs containing Er 3+ :LaF 3 nanocrystals were selected for the investigation on NLO, because of LaF 3 nanocrystals embedded in germanate oxyfluoride GCs are desirable hosts having merits of their broader transparency, lower phonon energy, higher RE ion solubility, weaker light scattering as well as better-matched refractive index than other hosts), 24-27 which might give effortless way of achieving "on-off" optical modulation for application in future integrated-optic circuits. 14 In the present work, we put forward a versatile approach to modulate the nonlinear transmittance of a single contribution for the reverse saturable absorption (RSA) effect. The effect of population densities of N 2 level is much bigger, and the spontaneous emission from the N 3 level to the N 2 and N 1 levels must be taken into account, which results in the larger ESA cross-section than the ground state absorption (GSA) cross-section. Through solving numerical...