A novel rational-fraction dispersion model is proposed for simulation of optical properties of arbitrary linear dispersive media over a wide wavelength range. A generally applicable method is proposed for estimating the parameters of this model. It is demonstrated that the rational-fraction dispersion model can fit the relative permittivity data of a material accurately and efficiently in a wide wavelength range. The new model is implemented in the finite-difference time-domain method and is applied as a powerful and computationally efficient tool for simulating nano-particles of dispersive materials in a wide wavelength range of light.
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