On 01/03/2018 01:07 PM, Priscilla Kelly wrote:
I would like to probe a material with a pulse whose frequency has an epsilon = -.3 + .002i. I have tested the system with an epsilon of 1 and everything works as expected.
A negative, frequency-independent epsilon will yield exponentially-growing fields as a consequence of violating causality (due to Kramers-Kronig relations). For details, see the related discussion in the documentation <https://meep.readthedocs.io/en/latest/FAQ/#why-does-my-simulation-diverge-if-0>. If you want to model materials with negative epsilon, you must add dispersion.
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