Dispersive Media and Metamaterials Changes

Changes regarding dispersive media and metamaterials in version 6.0 rev.4:

In previous versions of the software, non-standard definitions of plasma frequency f_p and collision frequency v_c for Drude and Lorentz dispersion models have been used. Now standard definitions are enforced, according to the formulae given in Sec.E 2.5.3 of QW-Editor Reference Guide.
In general, QuickWave software allows the user to set any values of media parameters. For dispersive media, there are several mutually related parameters, and their unphysical settings or sequence may lead to instabilities. Therefore a warning is now issued if

                                         eps_s < eps_inf

There are also limits on the admissible level of losses with respect to the FDTD time step Dt, from the viewpoint of acccuracy.
For Debye, the requirement is
                                         tau > 0.5 Dt
for Drude and Lorentz
                                         (2p v_c )^-1 > 0.5 Dt
Warnings are issued otherwise.

Several options have been implemented to allow suppressing dispersive behaviour of electric and/or magnetic media properties:
• For Lorentz, eps_s = eps_inf causes that the medium is considered as dielectric isotropic with frequency-independent permittivity eps_inf and conductivity Sigma.
• For Drude and Lorentz, f_p = 0 causes that the medium is considered as dielectric isotropic with frequency-independent permittivity eps_inf and conductivity Sigma.
• For Debye, tau=0 causes that the medium is considered as dielectric isotropic with frequency-independent permittivity eps_s and conductivity Sigma. If tau>0, eps_s = eps_inf causes that the medium is considered as dielectric isotropic with frequency-independent permittivity eps_inf and conductivity
                                                              Sigma + ((eps_s - eps_inf) / tau * eo).