On May 29, 2006, at 4:28 AM, K. Choi wrote:

Hi. Description about material dispersion in meep article has, " To implement a Drude model e(w), in which ωn is zero in the denominator, we just set ω_n to be a very small number (e.g. 1e-20) and make delta epsilon large to compensate in the numerator. " I don't understand this sentance. If I calculate a metal which has plasma frequency Wp = 1.1368e+16 and relaxation rate r = 9.7269e+13, how set this parameters into meep?

`take a look at http://ab-initio.mit.edu/wiki/index.php/Meep_Tutorial/`

`Material_dispersion`

`the form that meep wants for a (complex/dispersive) dielectric is: e`

`+ omega^2 de / ( omega^2 - w^2 - i w gamma).`

`the drude approximation goes as e - wp^2 / (w^2 + i w gamma). so, to`

`get them to agree set omega to be some small number (much smaller`

`than any w or sqrt(w gamma), so you can ignore it in the denominator`

`and then you get e - omega^2 de / (w^2 + i w^2 gamma), so finally set`

`wp^2 = omega^2 de, or de = wp^2 / omega^2.`

`finally, meep's units of w is always 2 pi c / a, where a is some`

`characteristic length in your problem. so omega and gamma must also`

`be in those units.`

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