Temperature-dependent Analytical Thermal Model for Endpumped Solid-state Lasers

Cini, Luigi; Bailey, Wendell; Yang, Y.; Mackenzie, Jacob I.

doi:10.1364/assl.2017.jm5a.5

Cited by 1 publication

(2 citation statements)

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“…We performed two best fits for two different temperature ranges around CT and RT. The first fit is based on measured data on a 1.3 at.% Nd:YAG sample in a temperature range of 40 K≤ T ≤175 K [10], while the second is based on published data of Sato et al [11] relating to 1.2 at.% Nd:YAG in a temperature range of 300 K≤ T ≤ 475 K. By finding the intersection of the two fitting curves, a common value of T 0 and k 0 = k(T 0 ) for the two temperature ranges can be found. The values of the parameters for ∼1 at.% Nd:YAG are, therefore, as follows: T 0 = 164.17 K, k 0 = 15.09 WK −1 m −1 , m CT = −1.77, and m RT = −0.75.…”

Section: Temperature Dependence Of Thermal Conductivitymentioning

confidence: 99%

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Analytical thermal model for end-pumped solid-state lasers

Cini

Mackenzie

2017

Appl. Phys. B

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their performance has capitalized on improving diode-laser brightness and power. Further power-scaling, however, is fundamentally limited by the thermo-optical properties of the gain medium and the induced optical distortions, primarily driven by the quantum defect between pump and the emission wavelengths. Alternatively, the geometry of the gain medium can be optimized to enhance thermal management and minimize the thermal-lensing effects, such as the thin-disk [1], fibre [2], or slab architectures [3], which have demonstrated multi-kW average powers. Nonetheless, for many applications, the end-pumped bulk architecture still holds an important position for its simplicity and robust performance.The basic design strategy for these lasers has been to try to mitigate the effects of the induced thermal-lensing and aberrations [4]. As such, it is important to understand the induced temperature distribution over the active volume of interest, that is, where the cavity mode passes through the excited region of the gain medium. Typically, this involves numerical simulations solving the heat equation with finiteelement algorithms, having almost completely replaced analytical solutions due to the complexity of the necessary assumptions made to obtain exact expressions. Analytical solutions, though, are unquestionably important: they highlight qualitative and quantitative features of underlying physical phenomena and provide more accurate solutions in far less time than numerical calculations, particularly if trying to perform parameter-dependence studies. One strict assumption generally made in determining the exact solution for the temperature profile along an end-pumped solid-state laser is that the thermal conductivity of the crystal is not significantly dependent on temperature [5]. While a reasonable assumption for many active media, operating at and above room temperature (RT), it is generally not valid when cooled to a cryogenic temperature (CT) [6]. Here, the gradient for Abstract Fundamentally power-limited by thermal effects, the design challenge for end-pumped "bulk" solid-state lasers depends upon knowledge of the temperature gradients within the gain medium. We have developed analytical expressions that can be used to model the temperature distribution and thermal-lens power in end-pumped solid-state lasers. Enabled by the inclusion of a temperature-dependent thermal conductivity, applicable from cryogenic to elevated temperatures, typical pumping distributions are explored and the results compared with accepted models. Key insights are gained through these analytical expressions, such as the dependence of the peak temperature rise in function of the boundary thermal conductance to the heat sink. Our generalized expressions provide simple and time-efficient tools for parametric optimization of the heat distribution in the gain medium based upon the material and pumping constraints.

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Section: Temperature Dependence Of Thermal Conductivitymentioning

confidence: 99%

“…Measured thermal conductivity dependence on temperature, after [10,11], and best fits using Eq. (1) Analytical thermal model for end-pumped solid-state lasers Page 3 of 14 273…”

Section: Figmentioning

confidence: 99%