Broadband subwavelength focusing of light using a passive drain

TL;DR

This paper introduces a broadband nanoabsorber that eliminates diffraction, enabling subwavelength light focusing and enhancement of local fields and gradients for ultrafast applications.

Contribution

It presents a novel broadband nanoabsorber design that achieves deep subwavelength focusing by engineering dielectric dispersion, surpassing standard illumination methods.

Findings

Focus of 6 fs pulse to 11 nm region

Significant enhancement of local field and gradient

Potential applications in ultrafast nonlinear spectroscopy

Abstract

Optical absorption is usually considered deleterious, something to avoid if at all possible. We propose a broadband nanoabsorber that completely eliminates the diffracting wave, resulting in a subwavelength enhancement of the field. Broadband operation is made possible by engineering the dispersion of the complex dielectric function. The local enhancement can be significantly improved compared to the standard plane wave illumination of a metallic nanoparticle. Our numerical simulation shows that an optical pulse as short as 6 fs can be focused to a 11 nm region. Not only the local field, but also its gradient are greatly enhanced, pointing to applications in ultrafast nonlinear spectroscopy, sensing and communication with deep-subwavelength resolution.