Defect state enhanced nonlinear absorption and optical limiting behaviour of erbium doped silver molybdate...

Transition metal based optical limiting materials have garnered significant attention due their crucial role in protecting sensitive optical system from high intense laser damage. Transition metal molybdates exhibits nonlinear optical (NLO) response, which attenuate highly intense light by transmitting light of desired intensity. Herein we report Silver molybdate (Ag₂MoO₄) nanostructures doped with erbium (Er) ions were successfully synthesized by simple co-precipitation technique. The proper incorporation of Er ions into the Ag₂MoO₄ lattice without altering the crystal structure was confirmed by XRD Analysis. The optical properties studied using UV-Vis absorption Spectroscopy exhibited maximum absorption in UV region and the absorption in the visible region is found to increase with the addition of Er ions into the host lattice. The XPS spectra confirmed the + 3 oxidation state of erbium and Ag⁰ state of silver. The NLO parameters such as, nonlinear absorption (NLA) and optical limiting (OL) was studied for the first time under 532 nm nanosecond laser excitation. Results suggest that erbium doped silver molybdate exhibited reverse saturable absorption originated from two photon absorption. The synthesized samples exhibited excellent nonlinear absorption and optical limiting performance. Also it is observed that with the addition of Er ions, the two photon absorption (2PA) is found to enhance from 0.85 × 10^-10 m/W (pure Ag₂MoO₄) to 6.223 × 10^-10 m/W for 0.5% Er doped sample. So, erbium doped silver molybdate nanostructures can be used for various tunable optoelectronic devices.