Mie scattering

Angular part of magnetic and electric vector spherical harmonics. Red and green arrows show the direction of the field. Generating scalar functions are also presented, only the first three orders are shown (dipoles, quadrupoles, octupoles).

A modern formulation of the Mie solution to the scattering problem on a sphere can be found in many books, e.g., J. A. Stratton's Electromagnetic Theory.[2] In this formulation, the incident plane wave, as well as the scattering field, is expanded into radiating spherical vector spherical harmonics. The internal field is expanded into regular vector spherical harmonics. By enforcing the boundary condition on the spherical surface, the expansion coefficients of the scattered field can be computed.

For particles much larger or much smaller than the wavelength of the scattered light there are simple and accurate approximations that suffice to describe the behavior of the system. But for objects whose size is within a few orders of magnitude of the wavelength, e.g., water droplets in the atmosphere, latex particles in paint, droplets in emulsions, including milk, and biological cells and cellular components, a more detailed approach is necessary.[3]

The Mie solution[4] is named after its developer, German physicist Gustav Mie. Danish physicist Ludvig Lorenz and others independently developed the theory of electromagnetic plane wave scattering by a dielectric sphere.

The formalism allows the calculation of the electric and magnetic fields inside and outside a spherical object and is generally used to calculate either how much light is scattered (the total optical cross section), or where it goes (the form factor). The notable features of these results are the Mie resonances, sizes that scatter particularly strongly or weakly.[5] This is in contrast to Rayleigh scattering for small particles and Rayleigh–Gans–Debye scattering (after Lord Rayleigh, Richard Gans and Peter Debye) for large particles. The existence of resonances and other features of Mie scattering makes it a particularly useful formalism when using scattered light to measure particle size.

Scattering of the plane wave, incidence direction is parallel to the z-axis, polarization is parallel to the x-axis, nanoparticle's radius is a

The scattering by a spherical nanoparticle is solved exactly regardless of the particle size. We consider scattering by a plane wave propagating along the z-axis polarized along the x-axis. Dielectric and magnetic permeabilities of a particle are ${\displaystyle \varepsilon _{1}}$ and ${\displaystyle \mu _{1}}$, and ${\displaystyle \varepsilon }$ and ${\displaystyle \mu }$ for the environment.

In order to solve the scattering problem,[3] we write first the solutions of the vector Helmholtz equation in spherical coordinates, since the fields inside and outside the particles must satisfy it. Helmholtz equation:

${\displaystyle \nabla ^{2}\mathbf {E} +{k}^{2}\mathbf {E} =0,\ \ \ \ \nabla ^{2}\mathbf {H} +{k}^{2}\mathbf {H} =0}$

in addition to the Helmholtz equation, the fields must satisfy the conditions ${\displaystyle \nabla \cdot \mathbf {E} =\nabla \cdot \mathbf {H} =0}$ and ${\displaystyle \nabla \times \mathbf {E} =i\omega \mu \mathbf {H} }$, ${\displaystyle \nabla \times \mathbf {H} =-i\omega \varepsilon \mathbf {E} }$. Vector spherical harmonics possess all the necessary properties, introduced as follows:

${\displaystyle \mathbf {M} _{^{e}_{o}mn}=\nabla \times \left(\mathbf {r} \psi _{^{e}_{o}mn}\right)}$ — magnetic harmonics (TE)

${\displaystyle \mathbf {N} _{^{e}_{o}mn}={\frac {\nabla \times \mathbf {M} _{^{e}_{o}mn}}{k}}}$ — electric harmonics (TM)

where

${\displaystyle {\psi _{emn}=\cos m\varphi P_{n}^{m}(\cos \vartheta )z_{n}({k}r)}}$

${\displaystyle {\psi _{omn}=\sin m\varphi P_{n}^{m}(\cos \vartheta )z_{n}({k}r)}}$

and ${\displaystyle P_{n}^{m}(\cos \theta )}$ — Associated Legendre polynomials, and ${\displaystyle z_{n}({k}r)}$ — any of the spherical bessel functions.

Next, we expand the incident plane wave in vector spherical harmonics:

${\displaystyle \mathbf {E} _{inc}=E_{0}e^{ikr\cos \theta }\mathbf {e} _{x}=E_{0}\sum _{n=1}^{\infty }i^{n}{\frac {2n+1}{n(n+1)}}\left(\mathbf {M} _{o1n}^{(1)}(k,\mathbf {r} )-i\mathbf {N} _{e1n}^{(1)}(k,\mathbf {r} )\right)}$

${\displaystyle \mathbf {H} _{inc}={\frac {-k}{\omega \mu }}E_{0}\sum _{n=1}^{\infty }i^{n}{\frac {2n+1}{n(n+1)}}\left(\mathbf {M} _{e1n}^{(1)}(k,\mathbf {r} )+i\mathbf {N} _{o1n}^{(1)}(k,\mathbf {r} )\right)}$

here the superscript ${\displaystyle (1)}$ means that in the radial part of the functions ${\displaystyle \psi _{^{e}_{o}mn}}$ are spherical Bessel functions. The expansion coefficients are obtained by taking integrals of the form

${\displaystyle {\frac {\int _{0}^{2\pi }\int _{0}^{\pi }\mathbf {E} _{inc}\cdot \mathbf {M} _{^{e}_{o}mn}^{(1)}\sin \theta d\theta d\varphi }{\int _{0}^{2\pi }\int _{0}^{\pi }|\mathbf {M} _{^{e}_{o}mn}^{(1)}|^{2}\sin \theta d\theta d\varphi }}}$

in this case, all coefficients at ${\displaystyle m\neq 1}$ are zero, since the integral over the angle ${\displaystyle \varphi }$ in the numerator is zero.

Then the following conditions are imposed:

1) Interface conditions on the boundary between the sphere and the environment (which allow us to relate the expansion coefficients of the incident, internal, and scattered fields)

2) The condition that the solution is bounded at the origin (therefore, in the radial part of the generating functions ${\displaystyle \psi _{^{e}_{o}mn}}$, Bessel spherical functions are selected for the internal field),

3) For a scattered field, the asymptotics at infinity corresponds to a diverging spherical wave (in connection with this, for the scattered field in the radial part of the generating functions ${\displaystyle \psi _{^{e}_{o}mn}}$ spherical Hankel functions of the first kind are chosen).

Scattered fields are written in terms of a vector harmonic expansion as

${\displaystyle \mathbf {E} _{s}=\sum _{n=1}^{\infty }E_{n}\left(ia_{n}\mathbf {N} _{e1n}^{(3)}(k,\mathbf {r} )-b_{n}\mathbf {M} _{o1n}^{(3)}(k,\mathbf {r} )\right)}$

${\displaystyle \mathbf {H} _{s}={\frac {k}{\omega \mu }}\sum _{n=1}^{\infty }E_{n}\left(a_{n}\mathbf {M} _{e1n}^{(3)}(k,\mathbf {r} )+ib_{n}\mathbf {N} _{o1n}^{(3)}(k,\mathbf {r} )\right)}$

here the superscript ${\displaystyle (3)}$ means that in the radial part of the functions ${\displaystyle \psi _{^{e}_{o}mn}}$ are spherical Hankel functions, and ${\displaystyle E_{n}={\frac {i^{n}E_{0}(2n+1)}{n(n+1)}}}$,

Internal fields:

${\displaystyle \mathbf {E} _{1}=\sum _{n=1}^{\infty }E_{n}\left(-id_{n}\mathbf {N} _{e1n}^{(1)}(k_{1},\mathbf {r} )+c_{n}\mathbf {M} _{o1n}^{(1)}(k_{1},\mathbf {r} )\right)}$

${\displaystyle \mathbf {H} _{1}={\frac {-k_{1}}{\omega \mu _{1}}}\sum _{n=1}^{\infty }E_{n}\left(d_{n}\mathbf {M} _{e1n}^{(1)}(k_{1},\mathbf {r} )+ic_{n}\mathbf {N} _{o1n}^{(1)}(k_{1},\mathbf {r} )\right)}$

${\displaystyle k={\frac {\omega }{c}}n}$ is the wave vector outside the particle ${\displaystyle k_{1}={\frac {\omega }{c}}{n_{1}}}$ is the wave vector in the medium from the particle material, ${\displaystyle n}$ and ${\displaystyle n_{1}}$ are the refractive indices of the medium and the particle,

After applying the interface conditions, we obtain expressions for the coefficients:

${\displaystyle c_{n}(\omega )={\frac {\mu _{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho )-\mu _{1}\left[\rho j_{n}(\rho )\right]'h_{n}(\rho )}{\mu _{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}}}$

${\displaystyle d_{n}(\omega )={\frac {\mu _{1}n_{1}n\left[\rho h_{n}(\rho )\right]'j_{n}(\rho )-\mu _{1}n_{1}n\left[\rho j_{n}(\rho )\right]'h_{n}(\rho )}{\mu n_{1}^{2}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu _{1}n^{2}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}},}$

${\displaystyle b_{n}(\omega )={\frac {\mu _{1}\left[\rho j_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'j_{n}(\rho )}{\mu _{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}}}$

${\displaystyle a_{n}(\omega )={\frac {\mu n_{1}^{2}\left[\rho j_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu _{1}n^{2}\left[\rho _{1}j_{n}(\rho _{1})\right]'j_{n}(\rho )}{\mu n_{1}^{2}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu _{1}n^{2}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}},}$

where

${\displaystyle \rho =ka}$

${\displaystyle \rho _{1}=k_{1}a}$ with ${\displaystyle a}$ being the radius of the sphere.

${\displaystyle j_{n}}$ and ${\displaystyle h_{n}}$ represent the spherical functions of Bessel and Hankel of the first kind, respectively.

Scattering and extinction cross-sections

Multipole decomposition spectrum of scattering cross-section by gold nanosphere with radius 100 nm

Multipole decomposition spectrum of scattering cross-section by nanosphere with radius 100 nm and refractive index n=4

Multipole decomposition spectrum of scattering cross-section by silicon nanosphere with radius 100 nm

Values commonly calculated using Mie theory include efficiency coefficients for extinction ${\displaystyle Q_{e}}$, scattering ${\displaystyle Q_{s}}$, and absorption ${\displaystyle Q_{a}}$.[6][7] These efficiency coefficients are ratios of the cross section of the respective process, ${\displaystyle \sigma _{i}}$, to the particle protected area, ${\displaystyle Q_{i}={\frac {\sigma _{i}}{\pi a^{2}}}}$, where a is the particle radius. According to the definition of extinction,

${\displaystyle \sigma _{e}=\sigma _{s}+\sigma _{a}}$ and ${\displaystyle Q_{e}=Q_{s}+Q_{a}}$.

The scattering and extinction coefficients can be represented as the infinite series:

${\displaystyle Q_{s}={\frac {2}{k^{2}a^{2}}}\sum _{n=1}^{\infty }(2n+1)(|a_{n}|^{2}+|b_{n}|^{2})}$

${\displaystyle Q_{e}={\frac {2}{k^{2}a^{2}}}\sum _{n=1}^{\infty }(2n+1)\Re (a_{n}+b_{n})}$

Kerker effect is a phenomenon in scattering directionality, which occurs when different multipole responses are presented and not negligible.

Particular (dipolar) case of the Kerker effect. The total electric field of the crossed magnetic and electric dipoles radiating in phase. The radiation pattern is asymmetric, in one direction the fields are mutually destroyed, and in the other, they add up.

In 1983, in the work of Kerker, Wang and Giles[10] the direction of scattering by particles with ${\displaystyle \mu \neq 1}$ was investigated. In particular, it was shown that for hypothetical particles with ${\displaystyle \mu =\varepsilon }$ backward scattering is completely suppressed. This can be seen as an extension to a spherical surface of Giles' and Wild's results for reflection at a planar surface with equal refractive indices where reflection and transmission is constant and independent of angle of incidence.[11]

In addition, scattering cross sections in the forward and backward directions are simply expressed in terms of Mie coefficients:[12][13]

${\displaystyle C_{sca}^{backward}={\frac {1}{a^{2}k^{2}}}{\bigg |}\sum _{n=1}^{\infty }{(2n+1)}(-1)^{n}(a_{n}-b_{n}){\bigg |}^{2}}$

${\displaystyle C_{sca}^{forward}={\frac {1}{a^{2}k^{2}}}{\bigg |}\sum _{n=1}^{\infty }{(2n+1)}(a_{n}+b_{n}){\bigg |}^{2}}$

For certain combinations of coefficients, the expressions above can be minimized.

So, for example, when terms with ${\displaystyle n>1}$ can be neglected (dipole approximation), ${\displaystyle (a_{1}-b_{1})=0}$, corresponds to the minimum in backscattering (magnetic and electric dipoles are equal in magnitude and are in phase, this is also called ‘first Kerker’ or ‘zero-backward intensity condition’[14]). And ${\displaystyle (a_{1}+b_{1})=0}$ corresponds to minimum in forward scattering, this is also called ‘second Kerker condition’ (or ‘near-zero forward intensity condition’). For the exact solution of the problem, it is necessary to take into account the contributions of all multipoles. The sum of the electric and magnetic dipoles forms Huygens source [15]

For dielectric particles, maximum forward scattering is observed at wavelengths longer than the wavelength of magnetic dipole resonance, and maximum backward scattering at shorter ones. .[16]

Later, other varieties of the effect were found. For example, the transverse Kerker effect, with nearly complete simultaneous suppression of both forward and backward scattered fields (side-scattering patterns),[17] optomechanical Kerker effect,[18] in acoustic scattering,[19] and also found in plants.[20]

There is also a short Video on YouTube with an explanation of the effect.

Green's function is a solution to the following equation:

${\displaystyle \nabla \times \nabla \times {\bf {\hat {G}}}(\omega ,\mathbf {r} ,\mathbf {r} ')=\left({\frac {\omega }{c}}\right)^{2}\varepsilon (\mathbf {r} ,\omega ){\bf {\hat {G}}}(\omega ,\mathbf {r} ,\mathbf {r} ')+{\bf {\hat {1}}}\delta (\mathbf {r} -\mathbf {r} '),}$

where ${\displaystyle {\hat {\bf {1}}}}$ — identity matrix ${\displaystyle \varepsilon (\mathbf {r} ,\omega )=\varepsilon _{1}(\omega )}$ для ${\displaystyle r<a}$, and ${\displaystyle \varepsilon (\mathbf {r} ,\omega )=\varepsilon }$ for ${\displaystyle r>a}$. Since all fields are vectorial, the Green function is a 3 by 3 matrix and is called a dyadic. If polarization ${\displaystyle \mathbf {P} (\mathbf {r} )}$ is induced in the system, when the fields are written as

${\displaystyle \mathbf {E} ^{\omega }({\mathbf {r} })=\omega ^{2}\mu \int \limits _{V}dV'{\hat {\bf {G}}}({\bf {r,r'}},k)\mathbf {P} ^{\omega }(\mathbf {r} ')}$

In the same way as the fields, the Green's function can be decomposed into vector spherical harmonics.[21] Dyadic Green's function of a free space а:[22]

${\displaystyle {\hat {\bf {G}}}^{0}({\mathbf {r} ,\mathbf {r} ',k})={\frac {\mathbf {e_{r}} \otimes \mathbf {e_{r}} }{k^{2}}}\delta (\mathbf {r} -\mathbf {r} ')+{\frac {ik}{4\pi }}\sum _{n=1}^{\infty }\sum _{m=0}^{n}(2-\delta _{m,0}){\frac {2n+1}{n(n+1)}}{\frac {(n-m)!}{(n+m)!}}\cdot }$

${\displaystyle \left\{{\begin{array}{l}\cdot {\Bigl (}(\mathbf {M} _{emn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{emn}^{(3)}[k,\mathbf {r} ']+\mathbf {M} _{omn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{omn}^{(3)}[k,\mathbf {r} '])+({\mathbf {N} }_{emn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{emn}^{(3)}[k,\mathbf {r} ']+\mathbf {N} _{omn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{omn}^{(3)}[k,\mathbf {r} ']){\Bigr )},{\text{if }}r<r'\\\cdot {\Bigl (}(\mathbf {M} _{emn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{emn}^{(1)}[k,\mathbf {r} ']+\mathbf {M} _{omn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{omn}^{(1)}[k,\mathbf {r} '])+({\mathbf {N} }_{emn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{emn}^{(1)}[k,\mathbf {r} ']+\mathbf {N} _{omn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{omn}^{(1)}[k,\mathbf {r} ']){\Bigr )},{\text{if }}r>r'\end{array}}\right.}$

In the presence of a sphere, the Green's function is also decomposed into vector spherical harmonics. Its appearance depends on the environment in which the points ${\displaystyle \mathbf {r} }$ and ${\displaystyle \mathbf {r} '}$ are located.[23]

When both points are outside the sphere (${\displaystyle r>a,r'>a}$):

${\displaystyle {\hat {\bf {G}}}^{00}({\mathbf {r} ,\mathbf {r} ',k,k_{1}})={\hat {\bf {G}}}^{0}({\mathbf {r} ,\mathbf {r} ',k})+{\frac {ik}{4\pi }}\sum _{n=1}^{\infty }\sum _{m=0}^{n}(2-\delta _{m,0}){\frac {2n+1}{n(n+1)}}{\frac {(n-m)!}{(n+m)!}}\cdot }$

${\displaystyle \cdot {\Bigl (}a_{n}^{(0)}(\omega )(\mathbf {M} _{^{e}_{o}mn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{^{e}_{o}mn}^{(3)}[k,\mathbf {r} '])+b_{n}^{(0)}(\omega )({\mathbf {N} }_{^{e}_{o}mn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{^{e}_{o}mn}^{(3)}[k,\mathbf {r} ']){\Bigr )}}$

where the coefficients are :

${\displaystyle a_{n}^{(0)}(\omega )={\frac {\mu /\mu _{1}\left[\rho _{1}j_{n}(\rho _{1})\right]'j_{n}(\rho )-\left[\rho j_{n}(\rho )\right]'j_{n}(\rho _{1})}{\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu /\mu _{1}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}},}$

${\displaystyle b_{n}^{(0)}(\omega )={\frac {n^{2}\mu _{1}/\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'j_{n}(\rho )-n_{1}^{2}\left[\rho j_{n}(\rho )\right]'j_{n}(\rho _{1})}{n_{1}^{2}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-n^{2}\mu _{1}/\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}}.}$

When both points are inside the sphere (${\displaystyle r<a,r'<a}$) :

${\displaystyle {\hat {\bf {G}}}^{11}({\mathbf {r} ,\mathbf {r} ',k,k_{1}})={\hat {\bf {G}}}^{0}({\mathbf {r} ,\mathbf {r} ',k_{1}})+{\frac {ik_{1}}{4\pi }}\sum _{n=1}^{\infty }\sum _{m=0}^{n}(2-\delta _{m,0}){\frac {2n+1}{n(n+1)}}{\frac {(n-m)!}{(n+m)!}}\cdot }$

${\displaystyle \cdot {\Bigl (}c_{n}^{(1)}(\omega )(\mathbf {M} _{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} ]\otimes {\mathbf {M} }_{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} '])+d_{n}^{(1)}(\omega )({\mathbf {N} }_{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} ]\otimes {\mathbf {N} }_{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} ']){\Bigr )},}$

Coefficients:

${\displaystyle c_{n}^{(1)}(\omega )={\frac {\mu _{1}/\mu \left[\rho h_{n}(\rho )\right]'h_{n}(\rho _{1})-\left[\rho _{1}h_{n}(\rho _{1})\right]'h_{n}(\rho )}{\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )-\mu _{1}/\mu \left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})}},}$

${\displaystyle d_{n}^{(1)}(\omega )={\frac {n_{1}^{2}\mu /\mu _{1}\left[\rho h_{n}(\rho )\right]'h_{n}(\rho _{1})-n^{2}\left[\rho _{1}h_{n}(\rho _{1})\right]'h_{n}(\rho )}{n^{2}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )-n_{1}^{2}\mu /\mu _{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})}}.}$

Source is inside the sphere and observation point is outside (${\displaystyle r>a,r'<a}$) :

${\displaystyle {\hat {\bf {G}}}^{01}({\mathbf {r} ,\mathbf {r} ',k,k_{1}})={\frac {ik_{1}}{4\pi }}\sum _{n=1}^{\infty }\sum _{m=0}^{n}(2-\delta _{m,0}){\frac {2n+1}{n(n+1)}}{\frac {(n-m)!}{(n+m)!}}\cdot }$

${\displaystyle \cdot {\Bigl (}a_{n}^{(1)}(\omega )(\mathbf {M} _{^{e}_{o}mn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} '])+b_{n}^{(1)}(\omega )({\mathbf {N} }_{^{e}_{o}mn}^{(3)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{^{e}_{o}mn}^{(1)}[k_{1},\mathbf {r} ']){\Bigr )}}$

coefficients:

${\displaystyle a_{n}^{(1)}(\omega )={\frac {\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho _{1})-\left[\rho _{1}h_{n}(\rho _{1})\right]'j_{n}(\rho _{1})}{\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )-\mu _{1}/\mu \left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})}},}$

${\displaystyle b_{n}^{(1)}(\omega )={\frac {nn_{1}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho _{1})-nn_{1}\left[\rho _{1}h_{n}(\rho _{1})\right]'j_{n}(\rho _{1})}{n^{2}\mu _{1}/\mu \left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )-n_{1}^{2}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})}}.}$

Source is outside the sphere and observation point is inside (${\displaystyle r<a,r'>a}$) :

${\displaystyle {\hat {\bf {G}}}^{10}({\mathbf {r} ,\mathbf {r} ',k,k_{1}})={\frac {ik}{4\pi }}\sum _{n=1}^{\infty }\sum _{m=0}^{n}(2-\delta _{m,0}){\frac {2n+1}{n(n+1)}}{\frac {(n-m)!}{(n+m)!}}\cdot }$

${\displaystyle \cdot {\Bigl (}c_{n}^{(0)}(\omega )(\mathbf {M} _{^{e}_{o}mn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {M} }_{^{e}_{o}mn}^{(3)}[k_{1},\mathbf {r} '])+d_{n}^{(0)}(\omega )({\mathbf {N} }_{^{e}_{o}mn}^{(1)}[k,\mathbf {r} ]\otimes {\mathbf {N} }_{^{e}_{o}mn}^{(3)}[k_{1},\mathbf {r} ']){\Bigr )}}$

coefficients:

${\displaystyle c_{n}^{(0)}(\omega )={\frac {\left[\rho h_{n}(\rho )\right]'j_{n}(\rho )-\left[\rho j_{n}(\rho )\right]'h_{n}(\rho )}{\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-\mu /\mu _{1}\left[\rho _{1}j_{n}(\rho _{1})\right]'h_{n}(\rho )}},}$

${\displaystyle d_{n}^{(0)}(\omega )={\frac {nn_{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho )-nn_{1}\left[\rho j_{n}(\rho )\right]'h_{n}(\rho )}{n_{1}^{2}\mu /\mu _{1}\left[\rho h_{n}(\rho )\right]'j_{n}(\rho _{1})-n^{2}\left[\rho _{1}j_{n}(\rho _{1})\right]'j_{n}(\rho )}}.}$

Mie solutions are implemented in a number of programs written in different computer languages such as Fortran, MATLAB, and Mathematica. These solutions solve for an infinite series, and provide as output the calculation of the scattering phase function, extinction, scattering, and absorption efficiencies, and other parameters such as asymmetry parameters or radiation torque. Current usage of the term "Mie solution" indicates a series approximation to a solution of Maxwell's equations. There are several known objects that allow such a solution: spheres, concentric spheres, infinite cylinders, clusters of spheres and clusters of cylinders. There are also known series solutions for scattering by ellipsoidal particles. A list of codes implementing these specialized solutions is provided in the following:

• Codes for electromagnetic scattering by spheres – solutions for a single sphere, coated spheres, multilayer sphere, and cluster of spheres;
• Codes for electromagnetic scattering by cylinders – solutions for a single cylinder, multilayer cylinders, and cluster of cylinders.

A generalization that allows a treatment of more generally shaped particles is the T-matrix method, which also relies on a series approximation to solutions of Maxwell's equations.

See also external links for other codes and calculators.

Mie theory is very important in meteorological optics, where diameter-to-wavelength ratios of the order of unity and larger are characteristic for many problems regarding haze and cloud scattering. A further application is in the characterization of particles by optical scattering measurements. The Mie solution is also important for understanding the appearance of common materials like milk, biological tissue and latex paint.

In 1986, P. A. Bobbert and J. Vlieger extended the Mie model to calculate scattering by a sphere in a homogeneous medium placed on flat surface. Like Mie model, the extended model can be applied to spheres with a radius close to the wavelength of the incident light.[36] There is a C++ code implementing Bobbert–Vlieger (BV) model.[37] Recent developments are related to scattering by ellipsoid.[38][39][40] The contemporary studies go to well known research of Rayleigh.[41]

• Computational electromagnetics
• Light scattering by particles
• List of atmospheric radiative transfer codes
• Codes for electromagnetic scattering by spheres
• Optical properties of water and ice

• Kerker, M. (1969). The scattering of light and other electromagnetic radiation. New York: Academic.
• Barber, P. W.; Hill, S. S. (1990). Light scattering by particles: Computational methods. Singapore: World Scientific. ISBN 978-9971-5-0813-5.
• Mishchenko, M.; Travis, L.; Lacis, A. (2002). Scattering, Absorption, and Emission of Light by Small Particles. New York: Cambridge University Press. ISBN 978-0-521-78252-4.
• Frisvad, J.; Christensen, N.; Jensen, H. (2007). "Computing the Scattering Properties of Participating Media using Lorenz-Mie Theory" (PDF). ACM Transactions on Graphics. 26 (3): 60. doi:10.1145/1276377.1276452.
• Wriedt, Thomas (2008). "Mie theory 1908, on the mobile phone 2008". Journal of Quantitative Spectroscopy & Radiative Transfer. 109 (8): 1543–1548. Bibcode:2008JQSRT.109.1543W. doi:10.1016/j.jqsrt.2008.01.009.
• Lorenz, Ludvig (1890). "Lysbevægelsen i og uden for en af plane Lysbølger belyst Kugle". Det Kongelige Danske Videnskabernes Selskabs Skrifter. 6 (6): 1–62.

• JMIE (2D C++ code to calculate the analytical fields around an infinite cylinder, developed by Jeffrey M. McMahon)
• SCATTERLIB: Collection of light scattering codes
• www.T-Matrix.de. Implementations of Mie solutions in FORTRAN, C++, IDL, Pascal, Mathematica and Mathcad
• ScatLab. Mie scattering software for Windows.
• Scattnlay, an open-source C++ Mie solution package with Python wrapper. Provides both, far-field and near-field simulation results for multilayered spheres.
• STRATIFY MatLab code of scattering from multilayered spheres in cases where the source is a point dipole and a plane wave. Description in arXiv:2006.06512
• Online Mie scattering calculator provides simulation results for bulk, core-shell, and multilayer spheres. Material parameters can be set by links to nk-data files from refractiveindex.info website. The source code is part of Scattnlay project freely available at GitHub
• Online Mie solution calculator is available, with documentation in German and English.
• Online Mie scattering calculator produces beautiful graphs over a range of parameters.
• phpMie Online Mie scattering calculator written on PHP.
• Mie resonance mediated light diffusion and random lasing.
• Mie solution for spherical particles.
• PyMieScatt, a Mie solution package written in Python.
• pyMieForAll, an open-source C++ Mie solution package with Python wrapper.