Perfect Absorption Of A Focused Light Beam By A Single Nanoparticle

Absorption of electromagnetic energy by a dissipative material is one of the most fundamental electromagnetic processes that underlies a plethora of applied problems, including sensing, radar detection, wireless power transfer, and photovoltaics. Common wisdom is that a finite dissipative object illuminated by a plane wave removes only a finite amount of the wave's energy flux, which is determined by the object's absorption cross-section. Thus, it is of fundamental interest to see if any far-field waveform can be perfectly absorbed by a finite object. Here, it is theoretically demonstrated that a precisely tailored light beam containing only far-field components can be perfectly absorbed by a finite scatterer on a substrate. The self-consistent scattering problem in the dipole approximation is analytically solved and finds a closed-form expression for the spatial spectrum of the incident field and the required complex polarizability of the particle. All analytical predictions are confirmed with full-wave simulations. The results introduce a qualitatively novel class of perfect absorption phenomena in electromagnetics and other wave processes.