The Combination of Drude and Lorentz Models
The function of fit of the relative permittivity of metal is written as the sum of the Drude and the Lorentz models:
In the following the angular frequency that is used in formula falls within the visible domain , corresponding to wavelengths in [400; 800] nm and photon energy in [1.55, 3.10] eV. Outside this domain, the quality of fitting can be impaired. This erratum gives us the opportunity to give better solutions to this hard problem of fitting, by investigating a wider space of search. The values of and are calculated according formula (8-9) in1, including the number of data used to compute the fitting equation.
Gold (Johnson & Christy2)
The proposed results of fitting of relative permittivities of metals are more accurate than those proposed in a previous paper4 and verify the criterion of compatibility with FDTD use. They can be used directly for any spectroscopic simulation5,6 and especially in FDTD codes, and for plasmonics7 and optimization where accurate positions of resonances should be found. The proposed method of fitting under constraint is a combination of PSO and Nelder-mead simplex methods appears to be efficient, even if the solution of the problem of fitting is not unique.