Broadband tunable near-infrared emission of Bi-doped composite germanosilicate glasses

Abstract

A broadband near-infrared (NIR) emission from Bi-doped lithium aluminum germanosilicate glasses is observed when excited by an 808 nm laser diode (LD). The intensity of the NIR emission increases primarily, and then decreases with increasing GeO₂ concentration. The optimized composition is 13Li₂O–23Al₂O₃–20GeO₂–43SiO₂–1Bi₂O₃ (mol%). The peak position and intensity of the NIR emission depend strongly on excitation wavelength. We attribute the emissions at 1100 nm and 1260 nm to ³P₁ → ³P₀ transition of Bi⁺ and ²D_3/2 → ⁴S_3/2 transition of Bi⁰, respectively. The proposed model explains the observed NIR luminescence phenomena of Bi-doped glasses and fibers, which was previously unknown.