Publications (76)
Electron phase space control in photonic chip-based particle acceleration
Roy Shiloh, Johannes Illmer, Tomáš Chlouba +5
Particle accelerators are essential tools in science, hospitals and industry. Yet, their costs and large footprint, ranging in length from meters to several kilometres, limit their…
Quantum interference visibility spectroscopy in two-color photoemission from tungsten needle tips
Ang Li, Yiming Pan, Philip Dienstbier +1
When two-color femtosecond laser pulses interact with matter, electrons can be emitted through various multiphoton excitation pathways. Quantum interference between these pathways…
Generation and Characterization of Attosecond Micro-Bunched Electron Pulse Trains via Dielectric Laser Acceleration
Norbert Schönenberger, Anna Mittelbach, Peyman Yousefi +2
Dielectric laser acceleration is a versatile scheme to accelerate and control electrons with the help of femtosecond laser pulses in nanophotonic structures. We demonstrate here th…
High-order above-threshold photoemission from nanotips controlled with two-color laser fields
Lennart Seiffert, Timo Paschen, Peter Hommelhoff +1
We investigate the process of phase-controlled high-order above-threshold photoemission from sharp metallic nanotips under bichromatic laser fields. Experimental photoelectron spec…
Gouy Phase-Related Effects in the Free-Space Optical Modulation of Free Electrons
Zhexin Zhao, Yiqi Fang, Mevlana Yunus UludaÄ +1
Modulating the free-electron wave function with light brings new opportunities to create attosecond electron pulse trains, to probe the quantum coherence of systems with significan…
A tip-based source of femtosecond electron pulses at 30keV
Johannes Hoffrogge, Jan-Paul Stein, Michael Krüger +5
We present a nano-scale photoelectron source, optimized towards ultrashort pulse durations and well-suited for time-resolved diffraction experiments. A tungsten tip, mounted in a s…
Demonstration of weak measurements, projective measurements, and quantum-to-classical transitions in ultrafast free electron-photon interactions
Yiming Pan, Eliahu Cohen, Ebrahim Karimi +8
How does the quantum-to-classical transition of measurement occur? This question is vital for both foundations and applications of quantum mechanics. Here, we develop a new measure…
Spatio-temporal sampling of near-petahertz vortex fields
Johannes Blöchl, Johannes Schötz, Ancyline Maliakkal +8
Measuring the field of visible light with high spatial resolution has been challenging, as many established methods only detect a focus-averaged signal. Here, we introduce a near-f…
Light-field driven currents in graphene
Takuya Higuchi, Christian Heide, Konrad Ullmann +2
Ultrafast electron dynamics in solids under strong optical fields has recently found particular attention. In dielectrics and semiconductors, various light-field-driven effects hav…
Scattering-asymmetry control with ultrafast electron wave packet shaping
Yuya Morimoto, Peter Hommelhoff, Lars Bojer Madsen
Scattering of a tightly focused electron beam by an atom forms one of the bases of modern electron microscopy. A fundamental symmetry breaking occurs when the target atom is displa…
Non-adiabatic ponderomotive effects in photoemission from nanotips in intense mid-infrared laser fields
Johannes Schötz, Sambit Mitra, Harald Fuest +10
Transient near-fields around metallic nanotips drive many applications, including the generation of ultrafast electron pulses and their use in electron microscopy. We have investig…
Multi-photon electron emission with non-classical light
Jonas Heimerl, Alexander Mikhaylov, Stefan Meier +4
Photon number distributions from classical and non-classical light sources have been studied extensively, yet their impact on photoemission processes is largely unexplored. In this…
Attosecond-fast internal photoemission
Christian Heide, Martin Hauck, Takuya Higuchi +4
The photoelectric effect has a sister process relevant in optoelectronics called internal photoemission. Here an electron is photoemitted from a metal into a semiconductor. While t…
Probing broken time-reversal symmetry with tailored-light photocurrents
Daniel M. B. Lesko, Tobias Weitz, Simon Wittigschlager +4
Light-field-driven photocurrents represent a powerful tool for generating photocurrents without external bias in light-matter systems that lack inversion symmetry. While these phot…
Attosecond control of electrons emitted from a nanoscale metal tip
Michael Krüger, Markus Schenk, Peter Hommelhoff
Attosecond science is based on steering of electrons with the electric field of well-controlled femtosecond laser pulses. It has led to, for example, the generation of XUV light pu…
Driving electrons at needle tips strongly with quantum light
Jonas Heimerl, Andrei Rasputnyi, Jonathan Pölloth +3
Attosecond science relies on driving electrons after photoemission with the strong optical field of a laser pulse, representing an intense classical coherent state of light. Bright…
Adiabaticity parameters for the categorization of light-matter interaction -- from weak to strong driving
Christian Heide, Tobias Boolakee, Takuya Higuchi +1
We investigate theoretically and numerically the light-matter interaction in a two-level system (TLS) as a model system for excitation in a solid-state band structure. We identify…
Transverse and longitudinal characterization of electron beams using interaction with optical near-fields
Martin Kozák, Joshua McNeur, Kenneth J. Leedle +9
We demonstrate an experimental technique for both transverse and longitudinal characterization of bunched femtosecond free electron beams. The operation principle is based on monit…
Coulomb interactions and the spatial coherence of femtosecond nanometric electron pulses
Stefan Meier, Peter Hommelhoff
The transverse coherence of electrons is of utmost importance in high resolution electron microscopes, point-projection microscopes, low-energy electron microscopy and various othe…
Inelastic ponderomotive scattering of electrons at a high-intensity optical travelling wave in vacuum
Martin Kozák, Timo Eckstein, Norbert Schönenberger +1
In the early days of quantum mechanics Kapitza and Dirac predicted that matter waves would scatter off the optical intensity grating formed by two counter-propagating light waves […
High Visibility in Two-Color Above-Threshold Photoemission from Tungsten Nanotips in a Coherent Control Scheme
Timo Paschen, Michael Förster, Michael Krüger +6
In this article we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between funda…
Atomic real-space perspective of light-field-driven currents in graphene
Yuya Morimoto, Yasushi Shinohara, Kenichi L. Ishikawa +1
When graphene is exposed to a strong few-cycle optical field, a directional electric current can be induced depending on the carrier-envelope phase of the field. This phenomenon ha…
Silicon dual pillar structure with a distributed Bragg reflector for dielectric laser accelerators: Design and fabrication
Peyman Yousefi, Joshua McNeur, Martin Kozák +5
Dielectric laser accelerators (DLAs) have proven to be good candidates for miniaturized particle accelerators. They rely on micro-fabricated dielectrics which are able to modulate…
A nanoscale vacuum-tube diode triggered by few-cycle laser pulses
Takuya Higuchi, Lothar Maisenbacher, Andreas Liehl +2
We propose and demonstrate a nanoscale vacuum-tube diode triggered by few-cycle near-infrared laser pulses. It represents an ultrafast electronic device based on light fields, expl…
Two-color coherent control of femtosecond above-threshold photoemission from a tungsten nanotip
Michael Förster, Timo Paschen, Michael Krüger +6
We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser puls…
Quantum Information Processing in Optical Lattices and Magnetic Microtraps
Philipp Treutlein, Tilo Steinmetz, Yves Colombe +9
We review our experiments on quantum information processing with neutral atoms in optical lattices and magnetic microtraps. Atoms in an optical lattice in the Mott insulator regime…
Dielectric-laser electron acceleration in a dual pillar grating with a distributed Bragg reflector
Peyman Yousefi, Norbert Schönenberger, Joshua McNeur +3
We report on the efficacy of a novel design for dielectric laser accelerators by adding a distributed Bragg reflector (DBR) to a dual pillar grating accelerating structure. This mi…
CEP-stable soliton-based pulse compression to 4.4 fs and UV generation at 800 kHz repetition rate
Alexey Ermolov, Christian Heide, Philip Dienstbier +4
We report generation of a femtosecond supercontinuum extending from the ultraviolet to the near-infrared and detection of its carrier-envelope phase variation by f-to-2f interferom…
Attosecond nanoscale near-field sampling
Benjamin Förg, Johannes Schoetz, Frederik Suessmann +15
The promise of ultrafast light field driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite fo…
Elements of a dielectric laser accelerator
Joshua McNeur, Martin Kozák, Norbert Schönenberger +11
The widespread use of high energy particle beams in basic research, medicine and coherent X-ray generation coupled with the large size of modern radio frequency (RF) accelerator de…
Quantum-coherent light-electron interaction in an SEM
Roy Shiloh, Tomas Chlouba, Peter Hommelhoff
The last two decades experimentally affirmed the quantum nature of free electron wavepackets by the rapid development of transmission electron microscopes into ultrafast, quantum-c…
Femtosecond laser-induced electron emission from nanodiamond-coated tungsten needle tips
Alexander Tafel, Stefan Meier, Juergen Ristein +1
We present femtosecond laser-induced electron emission from nanodiamond-coated tungsten tips. Based on the shortness of the femtosecond laser pulses, electrons can be photo-excited…
Probing of optical near-fields by electron rescattering on the 1 nm scale
Sebastian Thomas, Michael Krüger, Michael Förster +2
We present a new method of measuring optical near-fields within ~1 nm of a metal surface, based on rescattering of photoemitted electrons. With this method, we precisely measure th…
A microwave chip-based beam splitter for low-energy guided electrons
Jakob Hammer, Sebastian Thomas, Philipp Weber +1
We demonstrate the splitting of a low-energy electron beam by means of a microwave pseudopotential formed above a planar chip substrate. Beam splitting arises from smoothly transfo…
Boosting the efficiency of Smith-Purcell radiators using nanophotonic inverse design
Urs Haeusler, Michael Seidling, Peyman Yousefi +1
The generation of radiation from free electrons passing a grating, known as Smith-Purcell radiation, finds various applications including non-destructive beam diagnostics and tunab…
Fabrication and structural characterization of diamond-coated tungsten tips
Alexander Tafel, Mingjian Wu, Erdmann Spiecker +2
Coating metal nanotips with a negative electron affinity material like hydrogen-terminated diamond bears promise for a high brightness photocathode. We report a recipe on the fabri…
Imprinting the quantum statistics of photons on free electrons
Raphael Dahan, Alexey Gorlach, Urs Haeusler +8
The fundamental interaction between free electrons and light stands at the base of both classical and quantum physics, with applications in free-electron acceleration, radiation so…
Coherence in Microchip Traps
Philipp Treutlein, Peter Hommelhoff, Tilo Steinmetz +2
We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $5-1…
Laser-based acceleration of non-relativistic electrons at a dielectric structure
John Breuer, Peter Hommelhoff
A proof-of-principle experiment demonstrating dielectric laser acceleration of non-relativistic electrons in the vicinity of a fused-silica grating is reported. The grating structu…
Ponderomotive generation and detection of attosecond free-electron pulse trains
Martin Kozák, Norbert Schönenberger, Peter Hommelhoff
Atomic motion dynamics during structural changes or chemical reactions have been visualized by picosecond and femtosecond pulsed electron beams via ultrafast electron diffraction a…
Designs for a Quantum Electron Microscope
Pieter Kruit, Richard G. Hobbs, Chung-Soo Kim +11
One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe…
Attosecond physics in optical near fields
Jonas Heimerl, Stefan Meier, Anne Herzig +8
Attosecond science, the electron control by the field of ultrashort laser pulses, is maturing into lightfield-driven electronics, called petahertz electronics. Based on optical fie…
Cross-process interference in single-cycle electron emission from metal needle tips
Anne Herzig, Peter Hommelhoff, Eleftherios Goulielmakis +2
Though interference from different emission channels enabled a deeper understanding of strong-field photoemission in atoms and molecules, it remained out of reach for solids. Here,…
A Femtosecond Nanometer Free Electron Source
Peter Hommelhoff, Yvan Sortais, Anoush Aghajani-Talesh +1
We report a source of free electron pulses based on a field emission tip irradiated by a low-power femtosecond laser. The electron pulses are shorter than 70 fs and originate from…
Optical control of electrons in a Floquet topological insulator
Daniel M. B. Lesko, Tobias Weitz, Simon Wittigschlager +4
Light-dressed materials hold enormous potential for generating new electronic properties. The band structure resulting from light-dressing can exhibit starkly different quantum and…
Light-field control of real and virtual charge carriers
Tobias Boolakee, Christian Heide, Antonio Garzón-RamÃrez +3
Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be exci…
Alternating Phase Focusing for Dielectric Laser Acceleration
Uwe Niedermayer, Thilo Egenolf, Oliver Boine-Frankenheim +1
The concept of Dielectric Laser Acceleration (DLA) provides highest gradients among non-plasma particle accelerators. However, stable beam transport and staging have not been shown…
Quantum computing and quantum optics with recoiled free electrons
Maxim Sirotin, Andrei Rasputnyi, Tomáš Chlouba +2
Free electrons interacting coherently with optical fields provide a powerful platform for quantum simulation and quantum control. For kiloelectron-volt electron energies, even opti…
Coherent scattering of an optically-modulated electron beam by atoms
Yuya Morimoto, Peter Hommelhoff, Lars Bojer Madsen
Recent technological advances allowed the coherent optical manipulation of high-energy electron wavepackets with attosecond precision. Here we theoretically investigate the collisi…
Imaging the field inside nanophotonic devices
Tal Fishman, Urs Haeusler, Raphael Dahan +9
Controlling optical fields on the subwavelength scale is at the core of any nanophotonic device. Of particular interest are nanophotonic particle accelerators that promise a compac…
Sub-cycle temporal evolution of light-induced electron dynamics in hexagonal 2D materials
Christian Heide, Tobias Boolakee, Takuya Higuchi +1
Two-dimensional materials with hexagonal symmetry such as graphene and transition metal dichalcogenides} are unique materials to study light-field-controlled electron dynamics insi…
Coherent electron trajectory control in graphene
Christian Heide, Takuya Higuchi, Heiko B. Weber +1
We investigate coherent electron dynamics in graphene, interacting with the electric field waveform of two orthogonally polarized, few-cycle laser pulses. Recently, we demonstrated…
Large optical field enhancement for nanotips with large opening angles
Sebastian Thomas, Georg Wachter, Christoph Lemell +2
We theoretically investigate the dependence of the enhancement of optical near-fields at nanometric tips on the shape, size, and material of the tip. We confirm a strong dependence…
Strong-field above-threshold photoemission from sharp metal tips
Markus Schenk, Michael Krüger, Peter Hommelhoff
We present energy-resolved measurements of electron emission from sharp metal tips driven with low energy pulses from a few-cycle laser oscillator. We observe above-threshold photo…
Strong-Field Perspective on High-Harmonic Radiation from Bulk Solids
Takuya Higuchi, Mark I. Stockman, Peter Hommelhoff
Mechanisms of high-harmonic generation from crystals are described by treating the electric field of a laser as a quasi-static strong field. Under the quasi-static electric field,…
High spatial coherence in multiphoton-photoemitted electron beams
Stefan Meier, Takuya Higuchi, Manuel Nutz +2
Nanometer-sharp metallic tips are known to be excellent electron emitters. They are used in highest-resolution electron microscopes in cold field emission mode to generate the most…
Hanbury Brown and Twiss interference of electrons in free space from independent needle tip sources
Anton Classen, Raul Corrêa, Florian Fleischmann +4
We investigate two-electron interference in free space using two laser-triggered needle tips as independent electron sources, a fermionic realisation of the landmark Hanbury Brown…
Interaction of carrier envelope phase-stable laser pulses with graphene: the transition from the weak-field to the strong-field regime
Christian Heide, Tobias Boolakee, Takuya Higuchi +2
Ultrafast control of electron dynamics in solid state systems has recently found particular attention. By increasing the electric field strength of laser pulses, the light-matter i…
Dielectric laser acceleration of electrons in the vicinity of single and double grating structures - theory and simulations
John Breuer, Joshua McNeur, Peter Hommelhoff
Dielectric laser acceleration of electrons close to a fused-silica grating has recently been observed (Peralta et al., Nature 503, 91 (2013); Breuer, Hommelhoff, PRL 111, 134803 (2…
Few-electron correlations after ultrafast photoemission from nanometric needle tips
Stefan Meier, Jonas Heimerl, Peter Hommelhoff
Free electrons are essential in such diverse applications as electron microscopes, accelerators, and photo-emission spectroscopy. Often, space charge effects of many electrons are…
Optical gating and streaking of free-electrons with attosecond precision
Martin Kozak, Joshua McNeur, Kenneth J. Leedle +6
In this paper we present proof of principle experiments of an optical gating concept for free electrons. We demonstrate a temporal resolution of 1.2+-0.3 fs via energy and transver…
A spatially and temporally localized sub-laser-cycle electron source
Peter Hommelhoff, Catherine Kealhofer, Mark A. Kasevich
We present an experimental and numerical study of electron emission from a sharp tungsten tip triggered by sub-8 femtosecond low power laser pulses. This process is non-linear in t…
Microwave guiding of electrons on a chip
Johannes Hoffrogge, Roman Fröhlich, Mark A. Kasevich +1
Electrons travelling in free space have allowed to explore fundamental physics like the wave nature of matter, the Aharonov-Bohm and the Hanbury Brown-Twiss effect. Complementarily…
Highly coherent electron beam from a laser-triggered tungsten needle tip
Dominik Ehberger, Jakob Hammer, Max Eisele +4
We report on a quantitative measurement of the spatial coherence of electrons emitted from a sharp metal needle tip. We investigate the coherence in photoemission using near-ultrav…
Semitransparency in interaction-free measurements
Sebastian Thomas, Christoph Kohstall, Pieter Kruit +1
We discuss the effect of semitransparency in a quantum-Zeno-like interaction-free measurement setup, a quantum-physics based approach that might significantly reduce sample damage…
Deep Learning-Based Spatiotemporal Multi-Event Reconstruction for Delay Line Detectors
Marco Knipfer, Stefan Meier, Jonas Heimerl +2
Accurate observation of two or more particles within a very narrow time window has always been a challenge in modern physics. It creates the possibility of correlation experiments,…
Electron rescattering at metal nanotips induced by ultrashort laser pulses
Georg Wachter, Christoph Lemell, Joachim Burgdörfer +3
We report on the first investigation of plateau and cut-off structures in photoelectron spectra from nano-scale metal tips interacting with few-cycle near-infrared laser pulses. Th…
Charged particle guiding and beam splitting with auto-ponderomotive potentials on a chip
Robert Zimmermann, Michael Seidling, Peter Hommelhoff
We report guiding and manipulation of charged particle beams by means of electrostatic optics based on a principle similar to the electrodynamic Paul trap. We use hundreds of elect…
Roadmap for Quantum Nanophotonics with Free Electrons
F. Javier GarcÃa de Abajo, Albert Polman, Cruz I. Velasco +44
Over the past century, continuous advancements in electron microscopy have enabled the synthesis, control, and characterization of high-quality free-electron beams. These probes ca…
Tracing the phase of focused broadband laser pulses
Dominik Hoff, Michael Krüger, Lothar Maisenbacher +3
Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago an…
Imaging the transverse component of optical near-fields in resonant photonic structures
Petr Koutenský, Neli LaÅ¡toviÄková Streshkova, Stefanie Kraus +2
We report on imaging the optical near-fields in resonant periodic photonic structures with nanometer resolution using ultrafast 4D scanning transmission electron microscopy (U4DSTE…
Two-color coherent control in photoemission from gold needle tips
Philip Dienstbier, Timo Paschen, Peter Hommelhoff
We demonstrate coherent control of photoemission from a gold needle tip using a two-color laser field. The relative phase between a fundamental field and its second harmonic imprin…
Strong-Field Bloch Electron Interferometry for Band Structure Retrieval
Tobias Weitz, Christian Heide, Peter Hommelhoff
When Bloch electrons in a solid are exposed to a strong optical field, they are coherently driven in their respective bands where they acquire a quantum phase as the imprint of the…
Tracing attosecond electron emission from a nanometric metal tip
Philip Dienstbier, Lennart Seiffert, Timo Paschen +4
Solids exposed to intense electric fields release electrons through tunnelling. This fundamental quantum process lies at the heart of various applications, ranging from high bright…
Electronic coherence and coherent dephasing in the optical control of electrons in graphene
Christian Heide, Timo Eckstein, Tobias Boolakee +4
Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we mea…
Experimental considerations in electron beam transport on a nanophotonic chip using alternating phase focusing
Roy Shiloh, Tomas Chlouba, Peter Hommelhoff
Not long after the laser was invented, it has been marked as a candidate source of strong, high-frequency electromagnetic radiation for acceleration of particles. Indeed, while the…