Li2Gd4(MoO4)7 crystal preparation and spectral properties applied to 2.0 μm lasers

Abstract

A Tm³⁺/Ho³⁺ co-doped Li₂Gd₄(MoO₄)₇ (Tm/Ho:LGMO) crystal was grown using the Czochralski method. A systematic investigation of the structure characteristics, polarized absorption spectra, fluorescence spectra and lifetimes, and emission and gain cross-sections of this crystal was reported for the first time. The main spectroscopic parameters of Ho³⁺ ions in the grown crystal, such as J–O intensity parameters, line and oscillator strengths, spontaneous transition rates, fluorescence branching ratios and radiative lifetimes, were calculated using the Judd–Ofelt theory. Due to the statistical distributions of Li⁺, Gd³⁺ and vacancies, the absorption and emission spectra are strongly inhomogeneously broadened. The wide absorption bands at around 795 nm are quite desirable for the efficient pumping of AlGaAs laser diodes whose emission wavelengths usually change with the operating temperature. The broad emission bands from 1600 to 2200 nm allow wide tunability of laser oscillation. All the results reveal that the Tm/Ho:LGMO crystal is a promising gain medium for tunable and ultrafast pulse lasers at 2.0 μm.