Macro- and microscaled thermal poling in Eu3+-doped sodium tantalum phosphate glass

Abstract

Eu³⁺-doped sodium tantalum phosphate glass was synthesized by melt-quenching and its behavior under thermal poling/micropoling was investigated. The analysis of pristine glass indicates relatively high glass transition temperature (927ºC), refractive index (1.9) and transparency (~80%). The glass was thermally poled using homogeneous/microstructured electrodes under N₂, 250°C and voltage of 900 V. Considering macro-poling, Maker Fringes measurements confirmed Second Harmonic Generation (SHG) in the poled glass attributed to Electric Field Induced Second Harmonic (EFISH) with a sodium depletion thickness of 1.7μm and χ⁽²⁾ value of 0.72 pm/V. SHG/Raman/Luminescence correlated microscopy measurements allowed identification of the structural changes within the poled layer corresponding to SHG active layer under the anode surface. Changes in the Eu³⁺-emission were also identified in the poled layer. Considering micropoling, microstructured electrode allowed microprinting of patterns on the glass. Atomic Force Microscopy measurements evidenced spatial reliefs of 90 nm depth and presence of edge effects between the poled and non-poled areas. Edge effect was also observed by SHG-microscopy on the surface of the sample. SHG depends on the polarization state of the incident radiation, indicating that thermal micropoling induces both longitudinal and in-plane static electric fields. These results suggest a microscale control of the optical properties on this sodium tantalum phosphate glass.