Attosecond physics in optical near fields

TL;DR

This paper introduces NILES, a new spectral feature in electron spectra from nanostructures driven by ultrashort laser pulses, enabling detailed tracking and control of electron emission on attosecond time scales for petahertz electronics.

Contribution

It demonstrates the emergence of NILES in electron spectra, revealing sub-cycle electron dynamics and enabling enhanced electron control in optical near fields for the development of petahertz electronics.

Findings

NILES appears in the low energy region of electron spectra.

NILES allows tracking of electron emission on sub-cycle time scales.

High charge density electron bursts of 430 attoseconds were isolated.

Abstract

Attosecond science, the electron control by the field of ultrashort laser pulses, is maturing into lightfield-driven electronics, called petahertz electronics. Based on optical field-driven nanostructures, elements for petahertz electronics have been demonstrated. These hinge on the understanding of the electron dynamics in the optical near field of the nanostructure. Here we show near field-induced low energy stripes (NILES) in carrier-envelope phase-dependent electron spectra, a new spectral feature appearing in the direct electrons emitted from a strongly driven nanostructure, i.e., in the easily accessible energy region between 0 and a few electron volts. NILES emerge due to the sub-cycle sensitivity of ponderomotive acceleration of electrons injected into a strong near field gradient by a few-cycle optical waveform. NILES enables us to track the emission of direct and re-scattered electrons down to sub-cycle time-scales and to infer the electron momentum width at emission. Because NILES shows up in the direct part of the electrons, a large fraction of the emitted electrons can now be steered in new ways, facilitating the isolation of individual electron bursts with high charge density of 430 attosecond duration. These results not only substantially advance the understanding of attosecond physics in optical near fields, but also provide new ways of electron control for the nascent field of petahertz electronics.