New Insight into Collimated Plasmon Beam: Nondiffracting versus Linear Focusing

TL;DR

This paper introduces a new class of collimated plasmon beams created through in-plane diffraction with symmetric phase modulation, revealing their evolution from focusing to linear focusing and offering a flexible design scheme for beam modulation.

Contribution

It provides a novel understanding of collimated plasmon beams and proposes an intuitive diagram to distinguish between nondiffracting and linearly focusing beams, enabling advanced beam engineering.

Findings

Beams evolve from focusing to linear focusing as phase type changes.

An intuitive diagram clarifies the nature of plasmon beams.

A design scheme for modulating beam intensity is developed.

Abstract

We worked out a new group of collimated plasmon beams by the means of in-plane diffraction with symmetric phase modulation. As the phase type changes from 1.8 to 1.0, the beam undergoes an interesting evolution from focusing to a straight line. Upon this, an intuitive diagram was proposed to elucidate the beam nature and answer the question whether they are nondiffracting or linear focusing. Based on this diagram, we further achieved a highly designable scheme to modulate the beam intensity (e.g., 'lossless' plasmon). Our finding holds remarkable generality and flexibility in beam engineering and would inspire more intriguing photonic designs.