Thank you for your reply, Kaushik Quoting neal skinner <[email protected]>:
> Kaushik, > > You will find it both ways in various texts and the reason for the > difference is a little subtle. The value of a propagating wave changes with > time and distance traveled. Since in the time domain the value is periodic > (sinusoidal) it is usually supressed. > > If you assume an exp^(+ j omega t) time dependance, for a lossy > material, the imaginary part of refractive index for a lossy material will > be negative. > > If you assume an exp(- j omega t) time dependance, the imaginary part > of refractive index for a lossy material will be positive. > > If you look closely in the texts, the authors should state what version > of time depedence they have chosen to use (either is valid) and they should > use the approproate sign. > > I hope this helps. > > Good Luck! > > Neal > > > On Tue, Feb 16, 2010 at 2:36 PM, <[email protected]> wrote: > > > In the meep website, it is said that an complex epsilon of 3.4 + 0.101i at > > a > > frequency 0.42 (in your Meep units) > > can be modeled as (make medium (epsilon 3.4) (D-conductivity (/ (* 2 pi > > 0.42 > > 0.101) 3.4))) > > > > However, in most of the text book the complex epsilon is defined as > > > > epsilon = Re(epsilon) - Im(epsilon)*i > > > > I want to know if this is just a matter of sign convention? > > Meep reference says that the imaginary part of epsilon is associated with > > absorption loss in the material if it is positive. However, in the text > > books > > the imaginary part of epsilon is associated with absorption loss if it is > > negative. > > > > Thank you very much, > > Kaushik > > > > _______________________________________________ > > meep-discuss mailing list > > [email protected] > > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss > > > _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
