April 2016
Spotlight Summary by Ilya Shadrivov
Optical Fano resonances in a nonconcentric nanoshell
An undergraduate textbook on electromagnetism tells us that a small subwavelength spherical particle scatters light as a dipole. Present work shows us that this simple picture changes completely if an even smaller sphere of another material is placed asymmetrically inside the first sphere. Such a transformation leads to the excitation of multiple modes, or multipoles, within the sphere, leading to several interesting effects. In this Applied Optics article, Norton and Vo-Dinh performed analytical calculations of the multipoles and observed controllable interference of a dipole mode with a quadrupole mode. They present an approximate analytical method in which the number of modes used is truncated, which gives excellent agreement with full numerical simulations. This interference of two resonances leads to the formation of the so-called Fano resonance. Fano resonances have several interesting features, and they are known for their asymmetric shape, near-perfect cancellation of scattering at a certain frequency, and sharper spectral features than those of individual resonances. The properties of Fano resonances can be controlled by changing the interference between the interacting modes, and in the present work this is done by changing the offset of the inner sphere with respect to the centre of the outer sphere.
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Article Information
Optical Fano resonances in a nonconcentric nanoshell
Stephen J. Norton and Tuan Vo-Dinh
Appl. Opt. 55(10) 2611-2618 (2016) View: HTML | PDF