Light-dressed states under intense optical near fields

TL;DR

This study investigates how intense optical near fields influence the excitation dynamics of a quantum system, revealing high-order harmonic generation and parity-breaking effects due to inhomogeneous light-dressed states.

Contribution

It demonstrates that intense optical near fields induce high-order harmonic generation and enable forbidden transitions through altered, asymmetric dressed states.

Findings

High-order harmonic generations beyond third order observed.

Spatial inhomogeneity of ONF causes parity-breaking in dressed states.

Forbidden optical transitions become allowed due to asymmetry.

Abstract

We studied the excitation dynamics of a finite quantum system with an intense optical near field (ONF) from a perspective of light-dressed states. A simple model consisting of a single electron and a nano-sized short dipole source were employed. By calculating the time-dependent wave function subjected to the ONF, we demonstrated that the optical responses involved not only the first- and third-order but also the second-, fourth-order harmonic generations that were not obtained from conventional spatially homogeneous laser fields. In order to elucidate the origins of the exotic high-order harmonic generations, the dressed states altered by the ONF were explored. The result showed that the spatial distribution of the dressed states were significantly influenced by the ONF, making forbidden optical transitions to be allowed by parity breaking. This was caused by the spatial inhomogeneousness of the ONF, specifically its asymmetry, that was inherited to the dressed states.