Tunable, efficient, ultrafast broadband nonlinear optical properties of TiO2–loaded complex phosphate glasses

Abstract

On account of their excellent optical transparency from ultraviolet to far infrared spectral regions, phosphate glasses have become interesting nonlinear optical (NLO) materials for photonic nonlinear devices. However, small NLO coefficients tend to limit the usage of phosphate–based glasses in nonlinear photonic devices. Herein, we explored the NLO tunability in multicomponent phosphate glasses by increasing the coordination of orthophosphate (PO4)3– structural units with a great number of AlO4 groups through the addition of titanium dioxide (TiO2) in the composition. The NLO absorption and refraction characteristics were ascertained using open and closed–aperture Z–scan configurations respectively in a broadband spectral region ranging from 400 nm to 1200 nm under an ultrafast regime. The Z–scan results illustrate the increase of nonlinear susceptibility of glasses with titanium dioxide content in the composition due to the formation of non–π–conjugated orthophosphate groups which are in connection with AlO4 units. Typically, at 400 nm excitation, the NLO susceptibility improved by 119.91% upon addtion of 5 mol% of TiO2. The outcomes of the study acknowledge a new approach for conceiving highly NLO active phosphate glasses while maintaining deep–ultraviolet transparency through the polymerization of (PO4)3−groups. Consequently, the strategy explored in this work might pave the way for achieving the high NLO features of phosphate–based glasses to excel in their usage in data storage, signal transmission, optical limiting, and harmonic generation functionalities.