Study of thermal effects in an Nd doped phosphate glass laser rod

Measurement of thermal effects in LHG-8 Nd:glass laser rod during the transient and the cooling phases are presented. The induced thermal lensing is determined by passing a He-Ne probe beam through the rod and measuring the changes in the intensity of the probe beam transmitted through an out-of-focus iris placed near the focal plane of an external lens. Expression for the power of the Gaussian beam transmitted through a stressed laser rod placed between two crossed polarizers is derived. The values of the induced focal length corresponding to the temperature gradient deduced from the measurements of induced birefringence, an independent observable of thermal effects are obtained. These value are found to be in fairly good agreeement with the directly measured values.