Experimental determination of the thermo-optic coefficient (dn /dT ) and the effective stimulated emission cross-section (s e) of an a -axis cut 1.-at.?% doped Nd:GdVO4 crystal at 1.06 μm wavelength

Abstract

In this paper, we report the experimental determination of the thermo-optical coefficient (dn/dT) and the effective stimulated emission cross-section (σ_e) at 1064 nm for an a-axis cut 1.3-at.% doped Nd:GdVO4 crystal in a monolithic laser configuration. The pump-power-induced thermal lensing effect in the monolithic laser was used to determine these parameters. While measuring the dn/dT parameter, we also took into consideration the effect of pump-power-induced thermal expansion of the crystal. The dn/dT values obtained were 2.64-6 and 4.87×10^-6 K^-1, respectively, for directions parallel and perpendicular to the c-axis of the crystal. We show that the neglect of pump-power-induced thermal expansion of the crystal can overestimate the value of dn/dT by 30-50%. With the measured variation of the focal length of the thermal lens as a function of the absorbed pump power, we also computed the overlap integrals at the threshold pump power. These overlap integral values were used to estimate the product of the effective stimulated emission cross-section (σ_e) and the excited state lifetime (τ) of the Nd:GdVO4 crystal, which was found to be 1.476×10^-22 cm²s. With the reported values of τ for a 1.3-at.% doped Nd:GdVO4 crystal, we estimated the value of σ_e to be in the range 14.76×10^-19 to 16.4×10^-19 cm². The value of the effective stimulated emission cross-section measured in this way was found to be around two times higher in magnitude than earlier reported values measured by spectroscopic methods.