Determining the thermal lens focus of LD end-pumped Nd：GdVO4 solid-state laser with CCD detecting method

In order to study the thermal effect of Nd:GdVO4 crystal in LD end-pumped solid-state laser,a simply method to measure the thermal focal length with stable resonator is presented.By measuring M2 factor and the waist of output beam with CCD beam analyzer,the beam waist of the TEMOO mode can be deduced according to the law of multi-mode Gaussian beam propagation.Based on the ABCD matrix theory of stable resonator,the thermal focal length of the active medium is easily obtained.The experiment shows that the higher the pump power is,the smaller the thermal focal length is,and the worse the thermal effect influent the output beam quality.The thermal focal length of a LD end-pumped Nd:GdVO4 laser is measured and the experimental results agree with the theoretical predication.