Thermal modeling of continuous-wave end-pumped solid-state lasers

Innocenzi, M. E.; Yura, H. T.; Fincher, Curtis L.; Fields, R. A.

doi:10.1063/1.103083

Cited by 540 publications

(175 citation statements)

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“…(21) becomes which gives a temperature difference between the center and the edge of the rod equal to 24) is the same result as the one published by Innocenzi et al [14]. Figure 7 shows a comparison between our temperature profile and the one published by Innocenzi et al with the same parameters used for the tophat case (w = 300 μm is chosen).…”

Section: Gaussian Pumpingsupporting

confidence: 72%

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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: Gaussian Pumpingsupporting

confidence: 72%

“…It follows that the longitudinal derivatives in Eq. (2) with respect to the corresponding radial derivatives [14] can be neglected. Here, it is also assumed that the pump profile is axisymmetric, the behavior of the thermal conductivity k(T) of the crystal is described by Eq.…”

Section: Analytical Solutionmentioning

confidence: 99%

Analytical thermal model for end-pumped solid-state lasers

Cini

Mackenzie

2017

Appl. Phys. B

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“…The expression for thermal expansion coefficient α in the direction of vector n is [deduced from more common one [31]): 4 are the diagonal components of thermal expansion tensor in the optical indicatrix frame and α mg ¼-6.1 is the non-zero non-diagonal component [19] (the units are 10 À 6 K À 1 ).…”

Section: Basic Equationsmentioning

confidence: 99%

“…This change is highly non-uniform [2], especially for diode-pumping [3,4] with high localization of the heat release [5], so the material can act as a lens-like medium (thermal lens effect) [6]. It is recognized to be an important limitation of power scaling capabilities for solid-state lasers.…”

Section: Introductionmentioning

confidence: 99%

All-space existence and dispersion of athermal directions in monoclinic KY(WO4)2

Loiko

Филиппов

Кулешов

et al. 2014

Optics Communications

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a b s t r a c tThe analytical expressions for thermo-optic coefficients, dn/dT, for "fast" and "slow" light waves propagating along the arbitrary direction in a biaxial crystal are derived. On the basis of these expressions, the all-space analysis of existence of athermal directions is performed for monoclinic and biaxial KY(WO 4 ) 2 at 1.03 μm. The calculations are performed for an arbitrary light propagation direction and polarization (not restricted to the principal planes). The appearance of directions that can be athermal for both "fast" and "slow" waves is predicted. The dispersion of athermal directions is analyzed for visible and near-IR. The existence of upper and lower dispersion limits for athermal behavior of KY (WO 4 ) 2 is shown. It is shown that the optical indicatrix axes can be athermal itself at some light wavelengths. Wavelength-and temperature-dependent position of the optical axes of KY(WO 4 ) 2 is also determined.

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“…In the experiment, pump light from a custom built combination of six 808 nm laser-diode bars (details of which can be found in [10]), was focused to a beam radius of 34 µm with an M y 2  30 in the guided-axis, and end-coupled into the YAG/ Nd:YAG region, while in the unguided-axis the beam waist, radius 530 µm and M x 2  270, was positioned ~ 11 mm inside the waveguide. The laser resonator, illustrated in Figure 1, comprised a z-fold configuration (in the same plane as the unguided axis of the waveguide) formed by two highly reflective (HR) concave mirrors (R 2 , R 3 ), with radii of curvatures -300 mm and -100 mm respectively, and initially separated by the sum of their focal lengths.…”

Section: Experimental Setup and Measurementmentioning

confidence: 99%

Thermal lensing characterization of a high-radiance 946nm planar waveguide laser

Mackenzie

2012

SPIE Proceedings

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Abstract:We present the characterization of the in-plane thermal lens in a quasi-four-level Nd:YAG planar waveguide (PW) laser configured for high-radiance operation with an external stable-cavity. Our approach utilises the measurement of the laser's output irradiance distribution at the near-and far-field positions concurrently in order to obtain the "real time" beam propagation parameter and thus beam quality factor, M 2 . Coupled with the knowledge of the intra-cavity-thermallens-dependent beam sizes at an intra-cavity beam waist, the power dependent effective thermal lens focal length was characterized. A thermal lens focal length of >450 mm was obtained at all incident pump powers up to the maximum level of 87 W. This characterization enabled the build of a 29 W 946 nm PW laser with a record output radiance of 4.3 TWm -2 sr -1 .

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Thermal modeling of continuous-wave end-pumped solid-state lasers

Cited by 540 publications

References 1 publication

Analytical thermal model for end-pumped solid-state lasers

Analytical thermal model for end-pumped solid-state lasers

All-space existence and dispersion of athermal directions in monoclinic KY(WO4)2

Thermal lensing characterization of a high-radiance 946nm planar waveguide laser

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