A method measuring thermal lens focal length of all rays polarized in radial and tangential direction of high power Nd:YAG laser

摘要

A novel method is applied to measure the focal length of thermal lens of a CW Nd:YAG laser. Using resonator critical stable point G_(1) * G_(2)=0, by measuring output power as pumping power increasing, the laser rod thermal lens focal length f_(r) of all rays polarized in radial direction and the thermal lens focal length f_(θ) of all rays polarized in tangential direction can be calculated. The method can also be used to obtain the average effective thermal lens focal length f. The method requires no special equipment and is simple to implement. The measuring deviation of the method comparing with probe beam method is within the accuracy that is in the range of ±10%. It is less than the unstable-resonator method that is in the range of ±20%.