Anti-Stokes photoluminescence in Ga/Bi co-doped sol-gel silica glass.

Abstract

Unusual temperature dependence of the anti-Stokes photoluminescence (ASPL) at 734 nm was found in Ga/Bi co-doped sol-gel silica glass. While in the temperature range of 450-873 K, the behavior of ASPL is completely determined by the thermal population of the excited state levels, its intensity is continuously increasing with decreasing temperature in the range of 77-430 K. By measuring the pump power dependence of ASPL at 300 K, we show that the latter can be described via the two-step intracenter excitation process and subsequent relaxation. Based on the measurements of temperature dependence of the excitation spectra of near infrared band (at 1140 nm) and that corresponding to the ASPL (at 734 nm), we propose a simple rate equation model to explain the unusual behavior of ASPL.