Thank you so much for your reply. So if I use the Li 1980 reference for 1.2-1.4 um, which is in the transparent range, I should download the data and fit the Sellmeier coefficients, but I'm still not very clear how to convert that to Lorentz form.
On a separate account, I tried to load the default material library and got the following warning message, from materials_library import Si,SiO2 meep/geom.py:175: RuntimeWarning: Epsilon < 1 may require adjusting the Courant parameter. See the 'Numerical Stability' entry under the 'Materials' section of the documentation warnings.warn(eps_warning, RuntimeWarning) why would epsilon be <1 for these 2 materials? 18.07.2018, 11:41, "Ardavan Oskooi" <ardavan.osk...@gmail.com>: > On 07/18/2018 10:47 AM, Vince Lee wrote: > >> I'm new to Meep. I've installed pymeep and I'm running some of the tutorial >> examples. I have a question about the material library mentioned here >> (https://meep.readthedocs.io/en/latest/Materials/). The material library >> (https://github.com/stevengj/meep/tree/master/python/examples/materials_library.py) >> has Silicon but it only covers a wavelength range of 1.36 - 11 um, which >> misses the 1~1.4 um range I'm interested in. From the reference website >> https://refractiveindex.info/?shelf=main&book=Si&page=Salzberg there're many >> other models that covers that range, but I don't know how to get the >> necessary parameters to build the Lorentzian susceptibility profile of my >> own. > > The fitting parameters in the materials library are all based on > published references. Silicon has an indirect bandgap at approximately > 1.12 eV (wavelength of 1.1 um) at T=300K which makes fitting to a > Drude-Lorentz susceptibility profile particularly challenging (the > complex part is nearly negligible over a broad bandwidth). Note that the > Salzberg reference included in the materials library is based on the > Sellmeier coefficients which is valid for only a real permittivity and > can be readily converted into Drude-Lorentz form by setting γ=0. > > Perhaps you can find a reference which has the fitting parameters over > the missing wavelength range or try doing the fit on your own? > > _______________________________________________ > meep-discuss mailing list > meep-discuss@ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss _______________________________________________ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
