arXiv subjects

Markus Lippitz

Publications and source records attributed to Markus Lippitz.

15 recordsLinked to original sources

arXiv2025

The nonlinear limit of Babinet's Principle

Babinet's principle is a powerful tool for predicting the scattering behavior of planar structures where the solution for the complementary structure is already known. This makes it ubiquitous in the design of aperture antennas or metamaterials. Even for plasmonic nanostructures, a qualitative match of the behavior for complementary structures has been reported. Here, we discuss whether Babinet's principle can be extended to nonlinear scattering. We compare the third harmonic emission of plasmonic nanorods and complementary nanoslits by far field imaging and simulation. We find significantly different far field images, in agreement between experiment and simulation. We explain these differences by the higher spatial resolution at the third harmonic wavelength and by additional eddy currents in slits that are not present in rods. Within these limits, Babinet's principle can guide the design of inverted nonlinear plasmonic resonators, which promise to be more stable at high excitation power due to better thermal conductivity.

physics.optics↗

arXiv2025

Overcoming experimental obstacles in two-dimensional spectroscopy of a single molecule

Two-dimensional electronic spectroscopy provides information on coupling and energy transfer between excited states on ultrafast timescales. Only recently, incoherent fluorescence detection has made it possible to combine this method with single-molecule optical spectroscopy to reach the ultimate limit of sensitivity. The main obstacle has been the low number of photons detected due to limited photostability. Here we discuss the key experimental choices that allowed us to overcome these obstacles: broadband acousto-optic modulation, accurate phase-locked loops, photon-counting lock-in detection, delay stage linearization, and detector dead-time compensation. We demonstrate how the acquired photon stream data can be used to post-select detection events according to specific criteria.

physics.optics↗

arXiv2024

Fluorescence-detected two-dimensional electronic spectroscopy of a single molecule

Single-molecule fluorescence spectroscopy is a powerful method that avoids ensemble averaging, but its temporal resolution is limited by the fluorescence lifetime to nanoseconds at most. At the ensemble level, two-dimensional spectroscopy provides insight into ultrafast femtosecond processes such as energy transfer and line broadening, even beyond the Fourier limit, by correlating pump and probe spectra. Here, we combine these two techniques and demonstrate 2D spectroscopy of individual molecules at room temperature using the example of dibenzoterrylene (DBT) in a polymer matrix. We excite the molecule in a confocal microscope with a phase-modulated train of femtosecond pulses and detect the emitted fluorescence with single-photon counting detectors. Using a phase sensitive detection scheme, we were able to measure the nonlinear 2D spectra of most of the DBT molecules we studied. Our method is applicable to a wide range of single emitters and opens new avenues for understanding energy transfer in single quantum objects on ultrafast time scales.

physics.optics↗

arXiv2023

Intermediate Field Coupling of Single Epitaxial Quantum Dots to Plasmonic Waveguides

Key requirements for quantum plasmonic nanocircuits are reliable single-photon sources, high coupling efficiency to the plasmonic structures and low propagation losses. Self-assembled epitaxially grown GaAs quantum dots are close to ideal stable, bright and narrowband single-photon emitters. Likewise, wet-chemically grown monocrystalline silver nanowires are among the best plasmonic waveguides. However, large propagation losses of surface plasmons on the high-index GaAs substrate prevent their direct combination. Here, we show by experiment and simulation that the best overall performance of the quantum plasmonic nanocircuit based on these building blocks is achieved in the intermediate field regime with an additional spacer layer between the quantum dot and the plasmonic waveguide. High-resolution cathodoluminescence measurements allow a precise determination of the coupling distance and support a simple analytical model to explain the overall performance. The coupling efficiency is increased up to four times by standing wave interference near the end of the waveguide.

cond-mat.mes-hall↗

arXiv2020

Single Molecule Nonlinearity in a Plasmonic Waveguide

Plasmonic waveguides offer the unique possibility to confine light far below the diffraction limit. Past room temperature experiments of single quantum emitters coupled to such waveguides have mainly focused on efficient channelling of the spontaneous emission into waveguide modes after a linear optical excitation. However, only the simultaneous interaction of the emitter with multiple plasmonic fields would lead to functionality in a plasmonic circuit. Here, we demonstrate the nonlinear optical interaction of a single molecule and propagating plasmons. An individual terrylene diimide (TDI) molecule is placed in the nanogap between two single-crystalline silver nanowires. A visible wavelength pump pulse and a red-shifted depletion pulse travel along the waveguide, leading to stimulated emission depletion (STED) in the observed fluorescence. The efficiency increases by up to a factor of 50 compared to far-field excitation. Our study thus demonstrates remote nonlinear four-wave mixing at a single molecule with propagating plasmons. It paves the way towards functional quantum plasmonic circuits and improved nonlinear single-molecule spectroscopy.

physics.optics↗

arXiv2019

A single-crystalline silver plasmonic circuit for visible quantum emitters

Plasmonic waveguides are key elements in nanophotonic devices serving as optical interconnects between nanoscale light sources and detectors. Multimode operation in plasmonic two-wire transmission lines promises important degrees of freedom for near-field manipulation and information encoding. However, highly confined plasmon propagation in gold nanostructures is typically limited to the near-infrared region due to ohmic losses, excluding all visible quantum emitters from plasmonic circuitry. Here, we report on top-down fabrication of complex plasmonic nanostructures in single-crystalline silver plates. We demonstrate controlled remote excitation of a small ensemble of fluorophores by a set of waveguide modes and emission of the visible luminescence into the waveguide with high efficiency. This approach opens up the study of nanoscale light-matter interaction between complex plasmonic waveguides and a large variety of quantum emitters available in the visible spectral range.

physics.optics↗

arXiv2019

Symmetry-controlled second-harmonic generation in a plasmonic waveguide

A new concept for second-harmonic generation (SHG) in an optical nanocircuit is proposed. We demonstrate both theoretically and experimentally that the symmetry of an optical mode alone is sufficient to allow SHG even in centro-symmetric structures made of centro-symmetric material. The concept is realized using a plasmonic two-wire transmission-line (TWTL), which simultaneously supports a symmetric and an anti-symmetric mode. We first confirm the generated second-harmonics belong only to the symmetric mode of the TWTL when fundamental excited modes are either purely symmetric or anti-symmetric. We further switch the emission into the anti-symmetric mode when a controlled mixture of the fundamental modes is excited simultaneously. Our results open up a new degree of freedom into the designs of nonlinear optical components, and should pave a new avenue towards multi-functional nanophotonic circuitry.

physics.optics↗

arXiv2018

Coupling a single solid state quantum emitter to an array of resonant plasmonic antennas

Plasmon resonant arrays or meta-surfaces shape both the incoming optical field and the local density of states for emission processes. They provide large regions of enhanced emission from emitters and greater design flexibility than single nanoantennas. This makes them of great interest for engineering optical absorption and emission. Here we study the coupling of a single quantum emitter, a self-assembled semiconductor quantum dot, to a plasmonic meta-surface. We investigate the influence of the spectral properties of the nanoantennas and the position of the emitter in the unit cell of the structure. We observe a resonant enhancement due to emitter-array coupling in the far-field regime and find a clear difference from the interaction of an emitter with a single antenna.

physics.optics↗

arXiv2016

A quantum plasmonic nanocircuit on a semiconductor platform

Quantum photonics holds great promise for future technologies such as secure communication, quantum computation, quantum simulation, and quantum metrology. An outstanding challenge for quantum photonics is to develop scalable miniature circuits that integrate single-photon sources, linear optical components, and detectors on a chip. Plasmonic nanocircuits will play essential roles in such developments. Plasmonic components feature ultracompact geometries and can be controlled more flexibly and more energy-efficiently compared to conventional dielectric components due to strong field confinement and enhancement. Moreover, plasmonic components are compatible with electronic circuits, thanks to their deep subwavelength sizes as well as their electrically conducting materials. However, for quantum plasmonic circuits, integration of stable, bright, and narrow-band single photon sources in the structure has so far not been reported. Here we present a quantum plasmonic nanocircuit driven by a self-assembled GaAs quantum dot. The quantum dot efficiently excites narrow-band single plasmons that are guided in a two-wire transmission line until they are converted into single photons by an optical antenna. Our work demonstrates the feasibility of fully on-chip plasmonic nanocircuits for quantum optical applications.

physics.optics↗

arXiv2011

Nanoantenna-enhanced ultrafast nonlinear spectroscopy of a single gold nanoparticle

Optical nanoantennas are a novel tool to investigate previously unattainable dimensions in the nanocosmos. Just like their radio-frequency equivalents, nanoantennas enhance the light-matter interaction in their feed gap. Antenna enhancement of small signals promises to open a new regime in linear and nonlinear spectroscopy on the nanoscale. Without antennas especially the nonlinear spectroscopy of single nanoobjects is very demanding. Here, we present for the first time antenna-enhanced ultrafast nonlinear optical spectroscopy. In particular, we utilize the antenna to determine the nonlinear transient absorption signal of a single gold nanoparticle caused by mechanical breathing oscillations. We increase the signal amplitude by an order of magnitude which is in good agreement with our analytical and numerical models. Our method will find applications in linear and nonlinear spectroscopy of nanoobjects, ranging from single protein binding events via nonlinear tensor elements to the limits of continuum mechanics.

cond-mat.mes-hall↗

arXiv2011

Excitonic Fano Resonance in Freestanding Graphene

We investigate the role of electron-hole correlations in the absorption of freestanding monolayer and bilayer graphene using optical transmission spectroscopy from 1.5 to 5.5 eV. Line shape analysis demonstrates that the ultraviolet region is dominated by an asymmetric Fano resonance. We attribute this to an excitonic resonance that forms near the van-Hove singularity at the saddle point of the band structure and couples to the Dirac continuum. The Fano model quantitatively describes the experimental data all the way down to the infrared. In contrast, the common non-interacting particle picture cannot describe our data. These results suggest a profound connection between the absorption properties and the topology of the graphene band structure.

cond-mat.mes-hall↗

arXiv2010

Enhancing the optical excitation efficiency of a single self-assembled quantum dot with a plasmonic nanoantenna

We demonstrate how the controlled positioning of a plasmonic nanoparticle modifies the photoluminescence of a single epitaxial GaAs quantum dot. The antenna particle leads to an increase of the luminescence intensity by about a factor of eight. Spectrally and temporally resolved photoluminescence measurements prove an increase of the quantum dot's excitation rate. The combination of stable epitaxial quantum emitters and plasmonic nanostructures promises to be highly beneficial for nanoscience and quantum optics.

cond-mat.mes-hall↗

arXiv2009

Ultrafast time-resolved spectroscopy of 1D metal-dielectric photonic crystals

We study the all-optical switching behavior of one-dimensional metal-dielectric photonic crystals due to the nonlinearity of the free metal electrons. A polychromatic pump-probe setup is used to determine the wavelength and pump intensity dependence of the ultrafast transmission suppression as well as the dynamics of the process on a subpicosecond timescale. We find ultrafast (sub-picosecond) as well as a slow (millisecond) behavior. We present a model of the ultrafast dynamics and nonlinear response which can fit the measured data well and allows us to separate the thermal and the electronic response of the system.

cond-mat.other↗

arXiv2006

A Common-Path Interferometer for Time-Resolved and Shot-Noise-Limited Detection of Single Nanoparticles

We give a detailed description of a novel method for time-resolved experiments on single non-luminescent nanoparticles. The method is based on the combination of pump-probe spectroscopy and a common-path interferometer. In our interferometer, probe and reference arms are separated in time and polarization by a birefringent crystal. The interferometer, fully described by an analytical model, allows us to separately detect the real and imaginary contributions to the signal. We demonstrate the possibilities of the setup by time-resolved detection of single gold nanoparticles as small as 10 nm in diameter, and of acoustic oscillations of particles larger than 40 nm in diameter.

physics.optics↗

arXiv2005

Interferometric Time-Resolved Probing of Acoustic Modes in Single Gold Nanospheres

We measure the transient absorption of single gold particles with a common-path interferometer. The prompt electronic part of the signal provides high-contrast images for diameters as small as 10 nm. Mechanical vibrations of single particles appear on a longer timescale (period of 16 ps for 50 nm diameter). They reveal the full heterogeneity of the ensemble, and the intrinsic damping of the vibration. We also observe a lower-frequency mode involving shear. Ultra-fast pump-probe spectroscopy of individual particles opens new insight into mechanical properties of nanometer-sized objects.

cond-mat.other↗