Study on pump pulse characteristics of QCW diode-side-pumped Nd:YAG laser

The influence of pumping laser pulse on the property of quasi-continuous-wave diode-side-pumped Nd:YAG laser is investigated theoretically and experimentally here. Under remaining a fixed duty cycle, the average output power increases, and the corresponding thermal focal length shorten with the increase of the pump pulse duration, which attributes to the decrease of the ratio of pulse buildup time to the pulse duration. At a pump power of 146 W, the laser output power changes from 65.1 W to 81.2 W when the pulse duration is adjusted from 150 μs to 1000 μs, confirming a significant enhancement of 24.7%. A laser rate equation model incorporating the amplified spontaneous emission is also utilized and numerically solved, and the simulated results agree well with the experimental data.

The interferometric measurement of thermal lens effect in a LD pumped Tm-doped bulk laser

Directly measuring thermal focal length is important for designing and optimizing the mode locking oscillator, especially for a 2-μm mode-locking laser. In this paper, we propose a novel interferometric method for measuring the thermal focal length in a 2-μm mode-locking laser. This method could give a precise measurement of the thermal focal length inside a long-folded oscillator in both lasing and non-lasing operation. We also theoretically calculate the thermal focal length based on the temperature distribution inside the laser crystal, which matches well with the experimental result

Mitigation of Thermal Effects in End Pumping of Nd : YAG and Composite YAG/Nd : YAG Laser Crystas, Modelling and Experiments-=SUP=-1-=/SUP=-

In this work, we have presented a finite element (FE) numerical modelling simulations to study and analyze the thermal effects in Nd : YAG and composite YAG/Nd : YAG laser rods. We have calculated the temperature distributions, stress intensity and thermal focal lengths at different pump powers for both rods. The FE simulations showed that using composite laser rod of undoped cap reduces the maximum value of stress intensity and thermal focal length by ~35% and ~ 50%, respectively. We have verified the FE calculations experimentally by direct measurement of focal length of thermally induced lens by using Hartmann-Shack wavefront sensor. Good agreement was obtained between FE calculations and experimental measurements. Keywords: Nd : YAG lasers, Thermal lens, Wavefront sensing, solid state lasers.

Analysis of Thermal Effects within Cylindrical Shape Solid-State Laser Rod

In this work, a temperature-dependent analytical model was modified to predict the thermal effects of diode laser double–end-pumped cylindrical laser rod under Gaussian pump beam distribution. Heat load and temperature distribution were analyzed using the Kirchhoff integral transform method. Results show that a maximum temperature difference of approximately 69.61 K was obtained on each side face of the laser rod at a maximum power of 40 W (equally divided on each face). The total thermal focal length of approximately 34.64 mm was calculated under the Gaussian pumping profile. The finite element method code incorporated with well-verified software was used to numerically verify the obtained results, where the analytical and numerical results are highly matched. The results reveal that the total thermal focal length produced in a double–end-pumped geometry is two times less than that obtained from a single-end-pumped geometry.