Abstract
Unveiling the spatial and temporal dynamics of a light pulse interacting with nanosized objects is of extreme importance to widen our understanding of how photons interact with matter at the nanoscale and trigger physical and photochemical phenomena. An ideal platform to study light–matter interactions with an unprecedented spatial resolution is represented by plasmonics, which enables an extreme confinement of optical energy into sub-wavelength volumes. The ability to resolve and control the dynamics of this energy confinement on the time scale of a single optical cycle is at the ultimate frontier towards a full control of nanoscale phenomena. Here, we resolve in the time domain the linear behavior of a single germanium plasmonic antenna in the mid-infrared by measuring the complex optical field response in amplitude and phase with sub-optical-cycle precision, with the promise to extend the observation of light–matter interactions in the time domain to single quantum objects. Accessing this fundamental information opens a plethora of opportunities in a variety of research areas based on plasmon-mediated photonic processes and their coherent control, such as plasmon-enhanced chemical reactions and energy harvesting.
Highlights
A full understanding of light–matter interactions at the nanoscale can be enabled by resolving and correlating both the spatial and temporal structure of a light pulse interacting with nanoscale materials and molecules
We demonstrate that the oscillating optical field E0 of a light pulse interacting with a single plasmonic antenna and shaped by its resonance can be measured by femtosecond multi-THz time-domain spectroscopy (TDS) [52,53,54] combined with high-resolution confocal microscopy
All the double-rod antennas are fabricated from heavily doped germanium and feature arms with a thickness of 1.4 μm and a width of 1.0 μm and a gap width of 300 nm, while the arm length and the aspect ratio and resonance frequency are varied within the sample
Summary
A full understanding of light–matter interactions at the nanoscale can be enabled by resolving and correlating both the spatial and temporal structure of a light pulse interacting with nanoscale materials and molecules. From a spatial point of view, we have already reached a wide understanding of many nanoscale light–matter coupling phenomena in their ground state. In recent years plasmonics [1,2], and especially plasmonic nanoantennas [3,4,5,6,7], has received broad attention in nanophotonics, opening up valuable opportunities to enhance light–matter interactions for sensing [8,9,10,11], energy harvesting [12,13], and opto-electronics [14,15,16]. Owing to the large field enhancement over sub-diffraction limited volumes, various applications ranging from near-field microscopy [17,18] to ultra-sensitive material detection [19,20] and to the observation of higher-order optical
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