Temperature distribution and stress analysis of end pumped lasers under Gaussian pump profile
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Temperature distribution and stress analysis of end pumped lasers under Gaussian pump profile Mohammed Jalal AbdulRazzaq1 · Khalid S. Shibib1 · Sudad Issam Younis1 Received: 16 March 2020 / Accepted: 31 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Modified modeling of thermal effects within a dual end-pumped cylindrical shape laser medium was presented. The temperature distribution and the maximum hoop stress were determined by solving the heat conductance equation in a cylindrical medium. Two different incident beams of 0.6 mm waist radii were suggested, namely, effective √ and the Gaussian beam radii, where the effective beam radius is smaller by a factor of 2 than the Gaussian beam radius. Under these considerations, the radial temperature difference due to an effective beam radius was found to be 23% higher than that for a Gaussian beam radius. The calculations show that the pump power does not affect the location of the maximum hoop stress as the spot does. A discrepancy within 1% was obtained by comparing the obtained results with the experimental work in the literature. Keywords Dual-end pumped · Effective Gaussian beam · Laser damage · Thermal effects
1 Introduction In end-pumped lasers, the input face is under a high thermal loading and the upper limit on the critical input power density is determined by the fracture strength of the medium. Therefore, the temperature distribution inside the medium due to power and a spot diameter of the pump light usually dominate the system design considerations for the high average power laser. Both theoretical models and experimental settings were carried out by many researchers to reduce thermal effects generated due to high pumping power (AbdulRazzaq et al. 2019; Ahmed et al. 2018; Cini and Mackenzie 2017; El-Agmy and Al-Hosiny 2017; Ghadban et al. 2020; Kim et al. 2019; Liu et al. 2016; Mojahedi and Shekoohinejad 2018; Shen et al. 2015; Shibib et al. 2017). In this work, a modified thermal model was presented by considering two different beams, namely, effective and the Gaussian beam radii. Accordingly, the maximum temperature difference on each face was obtained taking into account the dependence of thermal conductivity on temperature, and the maximum hoop stress was obtained on each incident face of the medium by considering the * Mohammed Jalal AbdulRazzaq [email protected] 1
Laser and Optoelectronics Engineering Department, University of Technology –Iraq, Baghdad, Iraq
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dependence of thermal expansion coefficient on the temperature. A small discrepancy was obtained between our analysis and the experimental work in the literature.
2 Temperature distribution analysis The configuration illustrated in Fig. 1, concerns a cylindrical Nd:YAG laser rod with unequally absorbed pump power density from two end faces. The nonlinear heat equation was solved to estimate the temperature distribution and the maximum hoop stress with the help of
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