Flexible composition-dependent third-order optical nonlinearity of chalcogenide glasses within a Ge-Ga-S ternary system

In this work, we present a systemic study with respect to the third-order optical nonlinear (TONL) features of chalcogenide glasses (ChGs) within a germanium-gallium-sulfur (Ge-Ga-S, GGS) ternary system. The research outcomes show that the TONL attributes of GGS ChGs are highly tunable by glass composition, and the flexibility is higher than many other reported ChG systems. We have found that the TONL attributes of GGS ChGs depend remarkably on the deviation level of glass composition from chemical stoichiometry, which is associated with the presence of different types of defective units in the GGS glass network. The TONL dispersion of GGS ChGs is discovered to deviate from the classic theories based on crystalline semiconductors, as a result of the presence of multiple-steps absorption process occurred between gap states near the band gap, which renders the GGS ChGs applicable for various types of nonlinear optical functionalities.