Anisotropic stimulated emission cross-section measurement in Nd: YVO₄

As a crucial parameter in the design and analysis of laser performances, stimulated emission (SE) cross-section is currently considered to be dependent on several factors, such as temperatures and eigen-polarizations for anisotropic crystals. In contrast with these factors, impact of propagating directions upon SE cross-section has garnered less attention. In this paper, to investigate the SE cross-section in arbitrary propagating directions, fluorescence spectra for the transition ⁴F_3/2→⁴I_11/2 in Nd:YVO₄ are measured in different propagating directions. Based on Fuchtbauer-Ladenburg equation model, the propagating direction-dependent SE cross-section spectra in Nd:YVO₄ are obtained for the first time, to our best knowledge. A novel concept of anisotropic SE cross-section is proposed to interpret the propagating direction-dependent effect. The experiment results reveal that for an arbitrary propagating direction the SE cross-section of e light around 1064 nm can be expressed as a superposition from two principle axial propagating directions with a weight of plane projection.