Abstract
In the framework of Mie theory the involved electromagnetic fields are expanded in an infinite series of multipoles. In numerical computations the summation has to be terminated after a finite number of terms (the expansion order N), which unavoidably produces errors. On the other hand, it is known that the contributions of terms of order l with x < l < N, where x is the dimensionless size parameter, are highly localized, i.e., these contributions appear as sharp peaks in resonance spectra. We show that it is possible to specify the expansion order in a controlled manner to extract certain features from Mie spectra. This controlled modification of the expansion order can be used as a high-pass, low-pass or bandpass filter. Formulas that serve as linewidth (frequency) and resonance-order filters are given, and their usage is demonstrated.
© 1998 Optical Society of America
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