Mesoscale modeling of polycrystalline light transmission

Kuna, Lukasz; Mangeri, John; Gorzkowski, Edward P.; Wollmershauser, James A.; Nakhmanson, Serge

doi:10.1016/j.actamat.2019.06.001

Cited by 13 publications

(9 citation statements)

References 25 publications

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“…Each hexagonal crystallite is approximated as a cylinder with the same length and volume, corresponding to

l_{1, cyl} = 1.82 l_{1} a n d l_{2, cyl} = l_{2},

where l 1,cyl and l 2,cyl are the diameter and the length respectively. When considering adapting the results of the present idealized model to real materials, recent works [ 49,50 ] have shown that rigorous models for the distributions of crystallite size and orientation are required to accurately predict the scattering cross for the effective medium, with the potential for impressive agreement between model and experiment at the ≈10% level or better. In the present work we prioritize simplicity and analytical insight at the cost of such accuracy.…”

Section: Theorymentioning

confidence: 99%

Leveraging Anisotropy for Coupled Optimization of Thermal Transport and Light Transmission in Micro‐Structured Materials for High‐Power Laser Applications

Mishra

Garay

Dames

2020

Advcd Theory and Sims

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Maximum operating power densities in ceramic laser media scale with thermal conductivity k. This requires larger grain sizes in polycrystalline ceramics to reduce phonon scattering at grain boundaries. However, smaller grain sizes are preferred to minimize light scattering in the Rayleigh regime in polycrystals made from birefringent materials such as AlN and Al2O3, which are otherwise appealing for their high k. An optimization challenge arises from the opposite scaling laws governing the effects of grain sizes on k and light transmission. Here, this is tackled by introducing anisotropically microstructured materials (columnar/disk‐shaped grains) as the lasing media, and allowing orthogonal heat transfer and lasing directions. For columnar grains, larger grain sizes along the c‐axis help maintain high k for good heat dissipation, while preserving light transmission properties in the orthogonal lasing and pumping directions. Analytical models for the thermal conductivity in such structures are presented and verified using Monte‐Carlo ray‐tracing simulations. Similarly, an approximate Rayleigh–Gans–Debye model is used to predict light transmission and verified with exact simulations using FEM software. Finally, the tradeoff between thermal and optical phenomena is captured in a new anisotropic figure‐of‐merit tensor, which is optimized for the microstructure that maximizes lasing media performance in AlN and Al2O3 model systems.

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“…Each hexagonal crystallite is approximated as a cylinder with the same length and volume, corresponding to

l_{1, cyl} = 1.82 l_{1} a n d l_{2, cyl} = l_{2},

Section: Theorymentioning

confidence: 99%

Leveraging Anisotropy for Coupled Optimization of Thermal Transport and Light Transmission in Micro‐Structured Materials for High‐Power Laser Applications

Mishra

Garay

Dames

2020

Advcd Theory and Sims

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“…Further, the study of birefringence can be used in a finite-element model to evaluate the growth-induced residual stress, 8 or to completely characterize the photoelastic behavior of glasses, 9 or as an insight in functionally graded materials design. 10 The determination of the eigencouples of B(T) is one of the key points in such an analysis: In Sirotin and Shaskolskaya, 2 §.20, an approximate technique for their evaluation, based on the smallness of the difference between the eigenvectors of B(T) and those of B o , was proposed; we shall recall the main points of this procedure in Section 2.3.…”

Section: Introductionmentioning

confidence: 99%

“…Residual stresses are in the general case completely unknown, and indeed, the photoelastic‐based experimental techniques are one of the techniques widely used to detect their presence. Further, the study of birefringence can be used in a finite‐element model to evaluate the growth‐induced residual stress, 8 or to completely characterize the photoelastic behavior of glasses, 9 or as an insight in functionally graded materials design 10 …”

Section: Introductionmentioning

confidence: 99%

Some approximate relations in the photoelasticity of strongly anisotropic crystals

Davı́

2020

Math Methods in App Sciences

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The knowledge of the principal refractive indices and their dependence on the applied stress is the starting point for any experimental analysis of transparent crystals. Because for strongly anisotropic crystals and a general state of stress an explicit analytical solution can be difficult to obtain, then we need some approximated solutions. Here, we propose a coherent approximation procedure that generalizes results already obtained and give a simple example of application.

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“…19 Apart from experimental exploration, theoretical simulation is another important approach to investigate the pores' effect on ceramic transparency. 20,21 To simulate the light scattering of pores in ceramics, several theories and approximations have been developed. For example, the light scattering coefficients of pores were simulated using Mie theory by Zhang et al 19 Their conclusion suggested that the pores with diameter as large as visible light wavelength would cause a strong scattering.…”

Section: Introductionmentioning

confidence: 99%

“…Apart from experimental exploration, theoretical simulation is another important approach to investigate the pores’ effect on ceramic transparency 20,21 . To simulate the light scattering of pores in ceramics, several theories and approximations have been developed.…”

Section: Introductionmentioning

confidence: 99%

Light scattering by pores in YAG transparent ceramics simulated by DDA model

Yang

Duan

et al. 2020

J. Am. Ceram. Soc.

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Discrete dipole approximation (DDA) simulation was applied to study the effect of pores on light scattering in ceramics. The results of the DDA method were compared with that of Mie theory. The DDA method was approved to be reliable for calculating the scattering coefficients of YAG ceramics. The dependences of scattering coefficients on pore size and porosity, and the equal K sca (scattering coefficients) curves were all recalculated via DDA method. The results revealed that scattering coefficients increase with the increase of porosity and that small pores (diameters are about three-quarters of incident wavelength) produce much more light scattering than larger pores (diameters are several times larger than incident wavelength) at the same porosity. Furthermore, the equal K sca (scattering coefficients) curves showed that relatively high porosity will not sacrifice the critical pore size any more when pore sizes are several times larger than incident wavelength. This discovery perfects the scattering critical curves and has guiding significance for experiment. K E Y W O R D S DDA method, scattering, transparent ceramics, yttrium aluminum garnet How to cite this article: Yang Y, Ma N, Duan J, et al. Light scattering by pores in YAG transparent ceramics simulated by DDA model.

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Mesoscale modeling of polycrystalline light transmission

Cited by 13 publications

References 25 publications

Leveraging Anisotropy for Coupled Optimization of Thermal Transport and Light Transmission in Micro‐Structured Materials for High‐Power Laser Applications

Leveraging Anisotropy for Coupled Optimization of Thermal Transport and Light Transmission in Micro‐Structured Materials for High‐Power Laser Applications

Some approximate relations in the photoelasticity of strongly anisotropic crystals

Light scattering by pores in YAG transparent ceramics simulated by DDA model

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