mnpbem-material 0.1.1

Material dielectric models for plasmonic electrodynamics in MNPBEM-Python.

mnpbem-material

mnpbem-material implements dielectric function models commonly used in plasmonic simulations. The module provides simple analytical models and tabulated optical data for metallic materials such as Au, Ag, and Al.

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Implemented Formulations

1. Constant Dielectric Function

The simplest dielectric model assumes a wavelength-independent dielectric constant.

$$ [ \varepsilon(\lambda) = \varepsilon_0 ] $$

The corresponding wave number is

$$ [ k(\lambda) = \frac{2\pi}{\lambda}\sqrt{\varepsilon} ] $$

where

$$v* ( \varepsilon_0 )$$ : constant dielectric permittivity $$v* ( \lambda )$$ : wavelength

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2. Drude Model

The Drude model describes the optical response of free-electron metals.

$$ [ \varepsilon(\omega) = \varepsilon_\infty - \frac{\omega_p^2}{\omega(\omega + i\gamma)} ] $$

where

$$* ( \varepsilon_\infty )$$ : high-frequency dielectric constant $$* ( \omega_p )$$ : plasma frequency $$* ( \gamma )$$ : damping constant $$* ( \omega )$$ : angular frequency

Energy–Wavelength Conversion

The following relation is used to convert wavelength to photon energy:

$$ [ \omega_{eV} = \frac{EV_TO_NM}{\lambda_{nm}} ] $$

Material parameters for Au, Ag, and Al follow the formulation used in the MATLAB implementation:

Material/@epsdrude/init.m

from the original MNPBEM toolbox.

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3. Tabulated Material Model

For tabulated optical data ( (E, n, k) ), the dielectric function is computed as

$$ [ \varepsilon = (n + i k)^2 ] $$

where

$$* ( n )$$ : refractive index $$* ( k )v$$ : extinction coefficient

Interpolation is performed in the wavelength domain after converting tabulated energy values.

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Implementation

Core implementation:

src/mnpbem_material/models.py

Material datasets:

src/mnpbem_material/data/*.dat

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Dependencies

Runtime dependencies are installed automatically when the package is installed.

• numpy ≥ 1.24

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Example Usage

A runnable example is provided in:

examples/basic_usage.py

Run the example with:

python examples/basic_usage.py

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Author

GALIH RIDHO UTOMO [e-mail]