asasim: Adaptive sampling for electromagnetic simulations

For simulations of electromagnetic resonance spectra, where the locations of spectral features are unknown, and for wide-band simulations in general, a substantial number of wavelengths must be simulated for acceptable resolution, increasing computation time. This problem is exacerbated for spectra containing narrow-band features, as a high spectral resolution is required to even detect them. To address this challenge, a heuristic algorithm is presented for electromagnetic simulations, which adaptively refines the local resolution of spectral features during a simulation. The method supports parallel processing and plugs in with existing simulation systems, such as (RCWA). It can routinely reduce the computational load by two orders of magnitude.