Optical spectroscopy of Tm 3+ in a locally disordered Li 2Gd 4(MoO 4) 7 crystal: A candidate for tunable and ultrafast pulse lasers

Abstract

The optical properties of a locally disordered Tm 3+:Li 2Gd 4(MoO 4) 7 crystal have been investigated extensively to assess its feasibility of efficient ultrafast laser operation in the 2 μm spectral region. The main spectroscopic parameters relevant to laser applications have been evaluated by analyzing the polarized absorption spectra using the Judd–Ofelt theory. The cross-relaxation mechanisms between Tm 3+ levels have been applied to analyze the lifetimes of the 3F 4, 3H 4, and 1G 4 manifolds. The potential for producing subpicosecond laser pulses has been discussed on the basis of the calculated emission and gain cross-sections around 2 μm wavelength. The crystal exhibits broad optical bandwidths, large absorption/emission cross sections, and a long 3F 4 fluorescence lifetime. All these features indicate that the Tm 3+:Li 2Gd 4(MoO 4) 7 crystal is a promising gain medium for tunable and ultrafast (fs) pulse lasers.