Influence of Al2O3 on the photoluminescence and optical gain performance of Nd3+ doped germanate and tellurite glasses

Abstract

Abstract We investigated the influence of aluminum oxide, Al2O3, on the photoluminescence (PL) spectrum and optical gain (at 1064 m) of neodymium ion, Nd3+, doped tellurium and germanium oxide glasses with compositions TeO2 − ZnO and GeO2 − PbO, respectively. The PL properties of both materials were studied using a continuous-wave diode laser operating at 808 nm, in resonance with the Nd3+ transition 4I9/2 → 4F5/2. For samples containing Al2O3 it was observed PL intensity growth up to 30% in comparison with the samples without Al2O3. Luminescence decay (τm) from the 4F3/2 level was measured monitoring the 4F/32 → 4I11/2 transition. From calculations of the Judd–Ofelt parameters, the radiative lifetimes, the emission cross -section (σem) and the quantum efficiency of 4F3/2 → 4I11/2 transition were determined; the effective linewidth (Δλeff) was calculated to determine the gain bandwidth product (σem x Δeff), figure of merit (σem x τm) and saturation intensity (Is) parameters. Optical gain measurements were performed using a pump laser at 808 nm and a probe laser at 1064 nm. For the samples with Al2O3 the relative gain at 1064 nm reached ≈ 2.8 dB/cm (pump laser power: 400 mW) indicating an enhancement of about 65% for TeO2 − ZnO and 120% for GeO2 − PbO with respect to the samples without Al2O3. The optical gain enhancement is correlated to the PL intensity behavior and increases due to the presence of Al2O3 because the coordination environment of the Nd3+ changes and become more asymmetric leading to the growth of the emission cross-section. The present study shows that Nd3+ doped tellurium and germanium oxide glasses containing Al2O3 present particularly good prospects to be used as optical amplifiers at 1064 nm.