Quasi-four-level co-doped Tm/Ho gadolinium vanadate laser

Based on considering kinetic evolution of the emissions of both ions,the basic processes of energy transfer between thulium(Tm) and holmium(Ho) was analyzed,the quasi-four-level rate equation of thulium(Tm)/holmium(Ho) doped gadolinium vanadate(Tm/Ho:GdVO4) are given.The expression about threshold pump power and slope efficiency are concluded.At liquid nitrogen cooled temperature the operation of 2μm Tm/Ho:GdVO4 laser end-pumped by fiber-coupled laser diode(LD) is achieved experimentally.At 14W pump power the maximum 3.5W output power,optical-optical conversion efficiency of 25%,slope efficiency of 26.6% and pumping threshold of 838mW were obtained,theoretical results with experiment results are good agreement.The observed green fluorescence duo to result of up-conversion effect is also analyzed.