Research progress on thermal effect of LD pumped solid state laser

Even with the continuous improvement of laser-diode-pumped solid-state lasers, thermal effects remain a bottleneck to their further development. In high-power or high-energy lasers, irregular thermal effects result in serious additional losses that not only reduce laser power, but also damage optical components in the laser. For further development of high-energy, high-power and high-performance solid-state lasers, it is essential to effectively control adverse laser thermal effects. The thermal lens effect caused by temperature gradients and the end face deformation caused by uneven transverse temperature distribution are dominant parts of the thermal effect. This paper focuses on the control and treatment of the thermal lens effect in lasers and analyses the deformation of the end face caused by heat. The thermal effect treatment scheme discussed here is divided into three categories: (1) the improvement of pump characteristics, (2) optimisation of the medium layout and (3) adjustment of the resonator structure. The first method obtains ideal thermal lensing by changing the pump mode and pump light distribution. The second method disperses or partially offsets the influence of the thermal lens effect and end deformation by optimising the concentration, end shape and the number of gain medium. The third method compensates or makes proper use of the thermal lens effect by changing the cavity structure or by inserting appropriate optical elements in the cavity.