Diffraction of Ultrashort Pulse on a Nanoscale Conductive Cone

TL;DR

This paper theoretically demonstrates how to control nanoscale superfocusing of ultrashort pulses using radially polarized surface plasmon polariton modes on conical metallic tips, with numerical simulations showing pulse compression effects.

Contribution

It introduces a novel method for controlling ultrashort pulse focusing at the nanoscale via conical metallic structures and chirp manipulation, supported by detailed numerical simulations.

Findings

Negative chirp shortens pulse duration by ~40%

Spatial distribution depends on chirp, angle, and distance

Chirp can partially compensate wave dispersion

Abstract

Surface plasmon polariton is collective oscillation of the free electrons at metal dielectric interface. As a wave phenomenon, surface plasmon polaritons can be focused using appropriate excitation geometry of metallic structures. We theoretically demonstrate the possibility of controlling nanoscale short pulse superfocusing based on the generation of radially polarized surface plasmon polariton mode of conical metallic tip. Numerical simulation for femtosecond pulse propagation along a silver nano-needle is discussed. The spatial distribution for a near field strongly depends on a linear chirp of the laser pulse which can partially compensate the wave dispersion. Field distribution is calculated for different chirp values, opening angles and distances. For a pulse with a negative chirp, pulse duration becomes shorter with amplification ~40.