A simple technique for accurate characterization of thermal lens in solid state lasers

摘要

Thermal lensing in diode pumped solid state lasers can seriously affect laser performance and cause beam distortions resulting in degradation of beam quality. Estimating thermal lens is important in designing stable laser cavities with minimum laser mode size fluctuations and high output power. The common techniques used to estimate the thermal lens under lasing condition deploy a probe beam or a wave front sensor. Both these techniques need precise alignment and the laser beam quality factor has to be measured separately for thermal lens calculations. It is well-known that beam quality varies considerably at different pump intensities. We demonstrate a simple technique based on ABCD law for Gaussian beams that is capable of estimating the thermal lens accurately by taking into account the fluctuation of beam quality factor at various pump intensities. The technique is experimentally tested using a diode-pumped YbrKYW laser at different pump intensities.