Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields

Liebtrau, Matthias; Sivis, Murat; Feist, Armin; Lourenço-Martins, Hugo; Pazos-Pérez, Nicolás; Alvarez-Puebla, Ramón A.; Abajo, F. Javier García de; Polman, A.; Ropers, Claus

doi:10.1038/s41377-021-00511-y

Cited by 50 publications

(32 citation statements)

References 78 publications

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“…A recent study has partially verified this relation by exploring the spatial characteristics of EELS, CL, and PINEM for the same single gold nanostar. 168 For completeness, we provide the expression obtained for an isotropic dipolar scatterer (see eqs 1 and 8 ) under continuous-wave illumination conditions.…”

Section: Fundamentals Of Electron-beam Spectroscopiesmentioning

confidence: 99%

Optical Excitations with Electron Beams: Challenges and Opportunities

2021

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Free electron beams such as those employed in electron microscopes have evolved into powerful tools to investigate photonic nanostructures with an unrivaled combination of spatial and spectral precision through the analysis of electron energy losses and cathodoluminescence light emission. In combination with ultrafast optics, the emerging field of ultrafast electron microscopy utilizes synchronized femtosecond electron and light pulses that are aimed at the sampled structures, holding the promise to bring simultaneous sub-Å–sub-fs–sub-meV space–time–energy resolution to the study of material and optical-field dynamics. In addition, these advances enable the manipulation of the wave function of individual free electrons in unprecedented ways, opening sound prospects to probe and control quantum excitations at the nanoscale. Here, we provide an overview of photonics research based on free electrons, supplemented by original theoretical insights and discussion of several stimulating challenges and opportunities. In particular, we show that the excitation probability by a single electron is independent of its wave function, apart from a classical average over the transverse beam density profile, whereas the probability for two or more modulated electrons depends on their relative spatial arrangement, thus reflecting the quantum nature of their interactions. We derive first-principles analytical expressions that embody these results and have general validity for arbitrarily shaped electrons and any type of electron–sample interaction. We conclude with some perspectives on various exciting directions that include disruptive approaches to noninvasive spectroscopy and microscopy, the possibility of sampling the nonlinear optical response at the nanoscale, the manipulation of the density matrices associated with free electrons and optical sample modes, and appealing applications in optical modulation of electron beams, all of which could potentially revolutionize the use of free electrons in photonics.

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Section: Fundamentals Of Electron-beam Spectroscopiesmentioning

confidence: 99%

Optical Excitations with Electron Beams: Challenges and Opportunities

2021

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“…Beyond stationary imaging, the advent of in situ and time-resolved electron microscopy allows for the observation of transient phenomena and non-equilibrium dynamics 32 – 35 . In the form of photon-induced near-field electron microscopy (PINEM) 6 , ultrafast transmission electron microscopy (UTEM) permits quantitative, high-resolution imaging of nano-optical fields 7 , 36 – 38 . The underlying mechanism involves energy transfer between localized optical excitations and free electrons, modifying the state of the electron by generating discrete photon sidebands in a process termed stimulated inelastic electron-light scattering (IELS).…”

Section: Mainmentioning

confidence: 99%

Integrated photonics enables continuous-beam electron phase modulation

Henke

Raja

Feist

et al. 2021

Nature

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101

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Integrated photonics facilitates extensive control over fundamental light–matter interactions in manifold quantum systems including atoms1, trapped ions2,3, quantum dots4 and defect centres5. Ultrafast electron microscopy has recently made free-electron beams the subject of laser-based quantum manipulation and characterization6–11, enabling the observation of free-electron quantum walks12–14, attosecond electron pulses10,15–17 and holographic electromagnetic imaging18. Chip-based photonics19,20 promises unique applications in nanoscale quantum control and sensing but remains to be realized in electron microscopy. Here we merge integrated photonics with electron microscopy, demonstrating coherent phase modulation of a continuous electron beam using a silicon nitride microresonator. The high-finesse (Q0 ≈ 106) cavity enhancement and a waveguide designed for phase matching lead to efficient electron–light scattering at extremely low, continuous-wave optical powers. Specifically, we fully deplete the initial electron state at a cavity-coupled power of only 5.35 microwatts and generate >500 electron energy sidebands for several milliwatts. Moreover, we probe unidirectional intracavity fields with microelectronvolt resolution in electron-energy-gain spectroscopy21. The fibre-coupled photonic structures feature single-optical-mode electron–light interaction with full control over the input and output light. This approach establishes a versatile and highly efficient framework for enhanced electron beam control in the context of laser phase plates22, beam modulators and continuous-wave attosecond pulse trains23, resonantly enhanced spectroscopy24–26 and dielectric laser acceleration19,20,27. Our work introduces a universal platform for exploring free-electron quantum optics28–31, with potential future developments in strong coupling, local quantum probing and electron–photon entanglement.

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“…90 nm size colloids. While nanosphere size plays a role in determining the final enhancing properties [ 54 ], the largest optical intensifications are, nonetheless, achieved at the tips of sharp protruding features [ 55 , 56 ] and, even more so, at nanometer-sized gaps between metal nanoparticles (i.e., hot-spots) due to interparticle plasmon coupling [ 52 , 57 ]. This latter effect is plainly visualized in Figure 2 B–D, which compares the calculated electromagnetic fields in dimers and larger aggregates with that of their parental isolated nanosphere [ 58 ].…”

Section: Isolation and Characterization Of Exosomesmentioning

confidence: 99%

Surface-Enhanced Raman Scattering (SERS) Spectroscopy for Sensing and Characterization of Exosomes in Cancer Diagnosis

Guerrini

Garcia‐Rico

O’Loghlen

et al. 2021

Cancers

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Exosomes are emerging as one of the most intriguing cancer biomarkers in modern oncology for early cancer diagnosis, prognosis and treatment monitoring. Concurrently, several nanoplasmonic methods have been applied and developed to tackle the challenging task of enabling the rapid, sensitive, affordable analysis of exosomes. In this review, we specifically focus our attention on the application of plasmonic devices exploiting surface-enhanced Raman spectroscopy (SERS) as the optosensing technique for the structural interrogation and characterization of the heterogeneous nature of exosomes. We summarized the current state-of-art of this field while illustrating the main strategic approaches and discuss their advantages and limitations.

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Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields

Cited by 50 publications

References 78 publications

Optical Excitations with Electron Beams: Challenges and Opportunities

Optical Excitations with Electron Beams: Challenges and Opportunities

Integrated photonics enables continuous-beam electron phase modulation

Surface-Enhanced Raman Scattering (SERS) Spectroscopy for Sensing and Characterization of Exosomes in Cancer Diagnosis

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