Rapid calculation for many refractive indices

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An interesting idea was proposed to optimize multiple runs of iterative solver 
when only the refractive index is varied.

N.V. Budko and R.F. Remis, “Electromagnetic inversion using a reduced-order 
three-dimensional homogeneous model,” Inv. Probl. 20, S17-S26 (2004).
http://dx.doi.org/10.1088/0266-5611/20/6/S02

This is relevant for:
1) construction of databases of scattering properties of different particles.
2) calculation of absorption/scattering/etc. spectra of particles much smaller 
than the wavelength.

Original issue reported on code.google.com by yurkin on 6 Jan 2011 at 7:33