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

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 13Li(2)O-23Al(2)O(3)-20GeO(2)-43SiO(2)-1Bi(2)O(3) (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 P-3(1) -> P-3(0) transition of Bi+ and D-2(3/2) -> S-4(3/2) transition of Bi-0, respectively. The proposed model explains the observed NIR luminescence phenomena of Bi-doped glasses and fibers, which was previously unknown.