Excitation wavelength dependence of quantum efficiencies of Nd-doped glasses for solar pumped fiber lasers

摘要

The quantum efficiencies of the emission from the ~4F_(3/2)(R) level of Nd doped in tellurite glass were measured with an integrating sphere using natural sunlight (η_(ns)), simulated sunlight (η_(ns)), and 808 nm laser light (η_(808)), respectively. The radiative quantum efficiency (η_r) was estimated from the fluorescence lifetime (τ_f) and the radiative lifetime calculated by Judd-Ofelt analysis (τ_r). η_r was almost 100 % for x≤0.5 mol.%. η_(808) was 86 % for x=0.05 mol.% and decreased monotonically with increasing in x. η_(ns) had a peak at x=0.5 mol.% and the maximum was 33 %. It is thought absorption of the excitation light by the host glass limits the quantum efficiency of the tellurite glass under sunlight excitation. Therefore, it is important to reduce absorption of the tellurite glass host in order to realize efficient solar-pumped tellurite fiber lasers.