Günter Kewes

Herein, a tunnel‐current‐driven plasmonic nanoantenna for the generation of single photons is proposed. The proposal uses two constituents: 1) small gold nanoparticles that feature Coulomb blockade already at room temperature combined with an 2) self‐similar nanorod arrangement. The Coulomb blockade allows for single‐plasmon generation and the nanorod arrangement for an efficient transformation into photons. As the emission from such an electrically driven antenna follows its spectral scattering response, the color of single photons can be tuned by geometrical changes of the antenna over an extremely broad range far into the infrared. The calculations suggest high photon purities, repetition rates beyond, and efficiencies comparable to ordinary single‐photon sources based on emitters like color centers or heralded single‐photon sources, respectively. Given recent achievements in the field and the …

The confinement of surface plasmon polaritons (SPPs) offers strong field strengths also for longitudinal field components. Phenomena like spin‐momentum locking can thus be exploited for novel functionality in nanodevices. External control of transport or directional coupling of propagating SPPs would be highly interesting for applications. Herein, the coupling of noble metal and magnetic nanoparticles to a silver nanowire acting as SPP waveguide using a hybrid self‐assembly approach is demonstrated. A designated setup is reported to isolate and investigate magnetically controlled transport in such devices. Various configurations are measured to quantify the required sensitivity for the typically tiny magnet response at moderate strengths of the magnetic field. Although magnetic control cannot be achieved, the required improvements can be estimated based on a heuristic numerical model. It is suggested using …

Monolayer (1L) transition-metal dichalcogenides (TMDCs) are of strong interest in nanophotonics due to their narrow-band intense excitonic transitions persisting up to room temperature. When brought into resonance with surface plasmon polariton (SPP) excitations of a conductive medium, opportunities arise for studying and engineering strong light-matter coupling. Here, we consider a very simple geometry, namely a planar stack composed of a thin silver film, an Al 2 O 3 spacer, and a monolayer of W S 2. We perform total internal reflection ellipsometry, which combines spectroscopic ellipsometry with the Kretschmann-Raether-type surface plasmon resonance configuration. The combined amplitude and phase response of the reflected light at varied angles of incidence proves that despite the atomic thinness of 1 L-W S 2, the strong-coupling (SC) regime between A excitons and SPPs propagating in the thin Ag …

Light–matter coupling in plasmonic nanocavities has been widely studied in the past years. Yet, for core–shell particles, popular electromagnetic models that use the classical Lorentz oscillator to describe the shell predict extinction spectra with three maxima, if the plasmon and the shell absorption are in resonance. In contrast, experiments exhibit only two peaks, as also expected from simple quantum models of hybrid states. In order to reconcile the convenient and widely used classical electromagnetic description with experimental data, we connect it to the quantum world by conceiving a heuristic quantum model. Our model is based on the permittivity of a two-level system in a classical electric field derived from the optical Bloch equations. The light–matter coupling is included via the collective vacuum Rabi frequency Ω0. Using our model, we obtain excellent agreement with a series of experimental extinction …

Raman spectroscopy is a powerful technique to characterize materials. It probes non-destructively chemical composition, crystallinity, defects, strain and coupling phenomena. However, the Raman response of surfaces or thin films is often weak and obscured by dominant bulk signals. Here we overcome this limitation by placing a transferable porous gold membrane (PAuM) on top of the surface of interest. Slot-like nanopores in the membrane act as plasmonic slot antennas and enhance the Raman response of the surface or thin film underneath. Simultaneously, the PAuM suppresses the penetration of the excitation laser into the bulk, efficiently blocking the bulk Raman signal. Using graphene as a model surface, we show that these two simultaneous effects lead to an increase in the surface-to-bulk Raman signal ratio by three orders of magnitude. We find that 90% of the Raman enhancement occurs within the top 2.5 of the material, demonstrating truly surface-sensitive Raman scattering. To validate our approach, we analyze the surface of a LaNiO3 thin film. We observe a Raman mode splitting for the LaNiO3 surface-layer, which is spectroscopic evidence that the surface structure differs from the bulk. This result underpins that PAuM give direct access to Raman signatures of surfaces and their structural properties.

Sub-diffraction limited localization of fluorescent emitters is a key goal of microscopy imaging. Here, we report that single upconversion nanoparticles, containing multiple emission centres with random orientations, can generate a series of unique, bright and position-sensitive patterns in the spatial domain when placed on top of a mirror. Supported by our numerical simulation, we attribute this effect to the sum of each single emitter’s interference with its own mirror image. As a result, this configuration generates a series of sophisticated far-field point spread functions (PSFs), e.g. in Gaussian, doughnut and archery target shapes, strongly dependent on the phase difference between the emitter and its image. In this way, the axial locations of nanoparticles are transferred into far-field patterns. We demonstrate a real-time distance sensing technology with a localization accuracy of 2.8 nm, according to the atomic force …

Spin-momentum locking is a peculiar effect in the near-field of guided optical or plasmonic modes. It can be utilized to map the spinning or handedness of electromagnetic fields onto the propagation direction. This motivates a method to probe the circular dichroism of an illuminated chiral object. In this work, we demonstrate local, subdiffraction limited chiral coupling of light and propagating surface plasmon polaritons in a self-assembled system of a gold nanoantenna and a silver nanowire. A thin silica shell around the nanowire provides precise distance control and also serves as a host for fluorescent molecules, which indicate the direction of plasmon propagation. We characterize our nanoantenna–nanowire systems comprehensively through correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging. Three-dimensional numerical simulations support the …

In this manuscript we demonstrate the potential of a hybrid technology which combines single organic molecules as quantum light sources and dielectric chips. In particular, we discuss our approach based on evanescent coupling of dibenzoterrylene molecules to silicon nitride waveguides and show a coupling efficiency of up to 42±2% over both propagation directions. Our results open a novel path towards a fully integrated and scalable photon processing platform.

Vacuum fluctuations are a fundamental feature of quantized fields. It is usually assumed that observations connected to vacuum fluctuations require a system well isolated from other influences. In this work, we demonstrate that effects of the quantum vacuum can already occur in simple colloidal nano-assemblies prepared by wet chemistry. We claim that the electromagnetic field fluctuations at the zero-point level saturate the absorption of dye molecules self-assembled at the surface of plasmonic nano-resonators. For this effect to occur, reaching the strong coupling regime between the plasmons and excitons is not required. This intriguing effect of vacuum-induced saturation (VISA) is discussed within a simple quantum optics picture and demonstrated by comparing the optical spectra of hybrid gold-core dye-shell nanorods to electromagnetic simulations.

G02. 00011: Absolute quantum efficiency measurement of single photon emitters in hexagonal Boron NitrideAbstractPresenter:Niko Nikolay(Department of Physics, Humboldt University of Berlin)Authors:Niko Nikolay(Department of Physics, Humboldt University of Berlin)Noah Mendelsohn(School of Mathematical and Physical Sciences, University of Technology Sydney)Ersan Özelci(Department of Physics, Humboldt University of Berlin)Bernd Sontheimer(Department of Physics, Humboldt University of Berlin)Florian Böhm(Department of Physics, Humboldt University of Berlin)Günter Kewes(Department of Physics, Humboldt University of Berlin)Milos Toth(School of Mathematical and Physical Sciences, University of Technology Sydney)Igor Aharonovich(School of Mathematical and Physical Sciences, University of Technology Sydney)Oliver Benson(Department of Physics, Humboldt University of Berlin)Single photon …