Antiresonance-Like Behavior in Carrier-Envelope-Phase-Sensitive Optical-Field Photoemission from Plasmonic Nanoantennas

TL;DR

This paper investigates antiresonance-like features in CEP-sensitive photoemission from plasmonic nanoantennas, revealing how they depend on pulse energy and waveform shape, and proposing their use to probe ultrafast electron dynamics.

Contribution

It demonstrates the existence of antiresonance-like features in CEP-sensitive photocurrent and explains their origin using a quasi-static tunneling model, highlighting their potential for ultrafast electron emission studies.

Findings

Sharp dip and phase shift in CEP-sensitive photocurrent at critical pulse energy

Antiresonance-like features arise from competition between half-cycle emissions

Features are highly sensitive to the optical waveform shape

Abstract

Given the quasi-static nature of optical-field emission and the nontrivial dependence of the emission rate on the instantaneous electric field strength, the CEP-sensitive component of the emitted photocurrent is highly sensitive to the energy of the optical pulse, and should carry information about the underlying sub-cycle dynamics of electron emission. Here we examine CEP-sensitive photoemission from plasmonic gold nanoantennas excited with few-cycle optical pulses of increasing energy. We observe antiresonance-like features in the CEP-sensitive photocurrent; specifically, at a critical pulse energy, we observe a sharp dip in the magnitude of the CEP-sensitive photocurrent accompanied by a sudden shift of {\pi}-radians in the phase of the photocurrent. Using a quasi-static tunneling emission model, we find that these antiresonance-like features arise due to competition between electron emission from neighboring optical half-cycles, and that they are highly sensitive to the precise shape of the driving optical waveform at the surface of the emitter. As the underlying mechanisms that produce the antiresonance-like features are a general consequence of nonlinear, field-driven photoemission, the antiresonance-like features could be used to probe sub-optical-cycle, sub-femtosecond emission processes, not only from solid-state emitters, but also from gas-phase atoms and molecules. Beyond applications in the study of ultrafast, field-driven electron physics, an understanding of these antiresonance-like features will be critical to the development of novel photocathodes for future time-domain metrology and microscopy applications that demand both attosecond temporal and nanometer spatial resolution.