Optical limiting and nonlinear optical properties of silver nanoparticles embedded glasses containing rare-earth ions at 532 nm under nanosecond regime

Abstract

Efficacy of silver nanoparticles concentration and annealing durations on optical limiting and optical nonlinearities of borate based glasses bearing the composition (79.5–x)B₂O₃–15Na₂O–5La₂O₃–0.5Sm₂O₃–xAgCl (mol%) was assessed by Z-scan approach under the pumping of visible light (532 nm) in nanosecond regime. The dual photon absorption parameter (α₂) was elevated from 0.576 × 10⁻¹¹ to 1.201 × 10⁻¹¹ m/W with AgCl content from 0 to 0.5 mol%. This α₂ further raised to 1.964 × 10⁻¹¹ m/W when the optimized glass host heat treated at 450° C for 25 h. Similarly, the index of nonlinear refraction (n₂) was enhanced from 1.642 × 10⁻¹⁹ to 2.532 × 10⁻¹⁹ m²/W as the AgCl content increased from 0 to 0.5 mol%. This n₂ value in turn monotonously increased to 2.963 × 10⁻¹⁹ m²/W when optimized glass system annealed at 450° C for 25 h. The optical limiting threshold magnitude followed reverse trend compared to α₂ and n₂. The enhancement in nonlinear optical features and optical limiting efficiencies were related to field stimulated by Ag⁰ nanoparticles when excited with high energy radiation. However, the non-uniform local field generated when the glass nanocomposites heated for longer duration resulted the switching of nonlinear absorption. The nonlinear optical and optical limiting results infer the 0.5 mol% AgCl encompassing glass sample annelaed at 450 °C for 25 h is benificail for construction of power optical limiters to operate in the visible range.