Paris Tzallas

Foundation for Research and Technology - Hellas | forth · Division of Laser Interactions and Photonics

Strong--laser--field physics is a research direction that relies on the use of high-power lasers and has led to fascinating achievements ranging from relativistic particle acceleration to attosecond science. On the other hand, quantum optics has been built on the use of low photon number sources and has opened the way for groundbreaking discoveries...

We present a comprehensive theoretical investigation of high-order harmonic generation in H$_2^+$ molecular ions within a quantum optical framework. Our study focuses on characterizing various quantum optical and quantum information measures, highlighting the versatility of HHG in two-center molecules towards quantum technology applications. We dem...

Optical Schr\"odinger "cat" states created by superpositions of coherent light states, correspond to an optical analog of the Schr\"odinger's cat in his $\textit{Gedankenexperiment}$. These non-classical light states are generated by means of quantum state engineering methods, and they are considered as one of the main resources for fundamental tes...

Strong laser physics is a research direction that relies on the use of high-power lasers and has led to fascinating achievements ranging from relativistic particle acceleration to attosecond science. On the other hand, quantum optics has been built on the use of low photon number sources and has opened the way for groundbreaking discoveries in quan...

Strongly laser-driven quantum correlated many-body systems lead to the generation of light with exotic quantum features — the quantumness of a many-body system is imprinted on the state of the emitted light.

Intense laser-matter interactions are at the center of interest in research and technology since the development of high-power lasers. They have been widely used for fundamental studies in atomic, molecular, and optical physics, and they are at the core of attosecond physics and ultrafast optoelectronics. Although the majority of these studies have...

Light-matter entanglement plays a fundamental role in many applications of quantum information science. Thus, finding processes where it can be observed is an important task. Here, using a one-dimensional model, we address this matter by investigating theoretically the entanglement between light and electrons generated in the above-threshold ioniza...

In the present work we report on the current progress of the recently constructed GW attosecond extreme ultraviolet (XUV) source developed at the Institute of Electronic Structure and Laser of the Foundation for Research and Technology-Hellas (I.E.S.L-FO.R.T.H.). By the implementation of a compact-collinear polarization gating arrangement, the gene...

The quantum optical characterization of strongly laser-driven matter interactions may allow to extend current quantum technology platforms to unprecedented time and energy scales. In this work, we make a step forward in this direction by studying high-harmonic generation processes in solid-state systems under a quantum optical framework. We do this...

Two-XUV-photon double ionization of Ne, induced by an intense few-pulse attosecond train with a ∼4 fs envelope duration is investigated experimentally and theoretically. The experiment is performed at ELI-ALPS (Extreme Light Infrastructure Attosecond Light Pulse Source) utilizing the recently constructed 10 Hz gas phase high-order harmonic generati...

Two XUV-photon double ionization of Ne, induced by an intense few-pulse attosecond train with a ~ 4 fs envelope duration is investigated experimentally and theoretically. The experiment is performed at ELI-ALPS utilizing the recently constructed 10 Hz gas phase high-order harmonic generation SYLOS GHHG-COMPACT beamline. A total pulse energy up to ~...

In this article, we will discuss a possibility of a symbiosis for attophysics (AP) and quantum information (QI) and quantum technologies (QT). We will argue that within few years AP will reach Technology Readiness Level (RTL) 4-5 in QT, and will thus become a legitimate platform for QI and QT.

Ultrafast plasma dynamics play a pivotal role in the relativistic high harmonic generation, a phenomenon that can give rise to intense light fields of attosecond duration. Controlling such plasma dynamics holds key to optimize the relevant sub-cycle processes in the high-intensity regime. Here, we demonstrate that the optimal coherent combination o...

It was recently shown in [P. Stammer et al, arXiv:2206.04308 (2022)] that, in above-threshold ionization processes, the displacement generated in the quantum state of the electromagnetic field after the interaction with the atomic system, depends on the kinetic energy and emission direction of the generated photoelectrons. Since the electron can ge...

Intense laser-matter interactions are at the center of interest in research and technology since the development of high power lasers. They have been widely used for fundamental studies in atomic, molecular, and optical physics, and they are at the core of attosecond physics and ultrafast opto-electronics. Although the majority of these studies hav...

We present a theoretical demonstration on the generation of entangled coherent states and of coherent state superpositions, with photon numbers and frequencies orders of magnitude higher than those provided by the current technology. This is achieved by utilizing a quantum mechanical multimode description of the single- and two-color intense laser...

Recently, intensely driven laser-matter interactions have been used to connect the fields of strong laser field physics with quantum optics by generating nonclassical states of light. Here, we take a further key step and show the potential of strong laser fields for generating controllable high-photon-number coherent-state superpositions. This has...

Tunability of energetic highly-elliptical high-harmonics is demonstrated. Harmonics are generated in Ar gas, driven by intense two-color counter rotating laser electric fields, namely of the fundamental and second harmonic frequency. For the experiment a MAZEL-TOV-like device is used, combined with loose focusing geometry. By properly tuning the ce...

We present the results of microscopic and macroscopic simulations on electron quantum path interferences during high harmonic generation in atomic gas medium driven by various ultrashort chirped driving laser pulses.

Recently, using conditioning approaches on the high-harmonic generation process induced by intense laser-atom interactions, we have developed a new method for the generation of optical Schrödinger cat states (Lewenstein et al. in Nat Phys, 17 1104–1108, 2021. https://doi/10.1038/s41567-021-01317-w). These quantum optical states have been proven to...

We investigate the electron quantum path interference effects during high harmonic generation in atomic gas medium driven by ultrashort chirped laser pulses. To achieve that, we identify and vary the different experimentally relevant control parameters of such a driving laser pulse influencing the high harmonic spectra. Specifically, the impact of...

Recently we have demonstrated the quantum nature of light in strongly laser driven atoms, and we have shown how the process of high harmonic generation can be used for the creation of highly non-classical light states, in particular superpositions of two coherent states, i.e., optical Schr\"{o}dinger "cat" states [M. Lewenstein et al., Generation o...

The physics of intense laser–matter interactions1,2 is described by treating the light pulses classically, anticipating no need to access optical measurements beyond the classical limit. However, the quantum nature of the electromagnetic fields is always present³. Here we demonstrate that intense laser–atom interactions may lead to the generation o...

We present a theoretical demonstration on the generation of entangled coherent states and of coherent state superpositions, with photon numbers and energies orders of magnitude higher than those provided by the current technology. This is achieved by utilizing a quantum mechanical multimode description of the single- and two-color intense laser fie...

Recently, using conditioning approaches on the high-harmonic generation process induced by intense laser-atom interactions, we have developed a new method for the generation of optical Schr\"odinger cat states (M. Lewenstein et al., arXiv:2008.10221 (2020)). These quantum optical states have been proven to be very manageable as, by modifying the co...

We investigate the electron quantum path interference effects during high harmonic generation in atomic gas medium driven by ultrashort chirped laser pulses. To achieve that, we identify and vary the different experimentally relevant control parameters of such a driving laser pulse influencing the high harmonic spectra. Specifically, the impact of...

We measure for the first time the duration of long-quantum path EUV high harmonics produced in xenon gas. The long-quantum path contribution to the high-harmonic signal was carefully controlled by employing a two-colour driving laser field and a high-harmonic spatial selection in the far field, over a range of $18-25\,eV$ in photon energy. To chara...

In this study the generation of energetic coherent extreme ultraviolet (XUV)radiation with controlled polarization, is reported. The XUV radiation resultsfrom the process of high harmonic generation (HHG), in a gas phase atomicmedium, driven by an intense two-color circularly polarized counter-rotating laser field, under loose focusing geometry con...

Quantum-optical spectrometry is a recently developed shot-to-shot photon correlation-based method, namely using a quantum spectrometer (QS), that has been used to reveal the quantum optical nature of intense laser-matter interactions and connect the research domains of quantum optics (QO) and strong laser-field physics (SLFP). The method provides t...

Quantum-optical spectrometry is a recently developed shot-to-shot photon correlation-based method, namely using a quantum spectrometer (QS), that has been used to reveal the quantum optical nature of intense laser–matter interactions and connect the research domains of quantum optics (QO) and strong laser-field physics (SLFP). The method provides t...

The interpretation of experimental data from novel mid-infrared few-cycle laser sources requires an understanding of ionization mechanisms and knowledge about related ion yields. Experimental studies have indicated sequential double ionization as the dominant process above 1014 W cm−2. These results contradict a recent prediction that in this spect...

Signatures of strong-field effects induced by an intense attosecond pulse train, synthesized by the superposition of a Ti:sapphire laser high-order harmonics are observed in atomic two-photon ionization. Ponderomotive shifts in the photoelectrons’ kinetic energies have been measured in the non-resonant two-photon ionization of Helium atoms induced...

Electron quantum path interferences in strongly laser-driven aligned molecules and their dependence on the molecular alignment is an essential open problem in strong-field molecular physics. Here, we demonstrate an approach which provides direct access to the observation of these interference processes. The approach is based on the combination of t...

High-harmonic generation is one of the most fundamental processes in strong laser-field physics that led to countless achievements in atomic physics and beyond. However, a rigorous quantum electrodynamical picture of the process has never been reported. Here, we rigorously prove theoretically and experimentally that the quantum state of the driving...

Recent developments in extreme ultraviolet (XUV) and x-ray radiation sources have pushed pulse energies and durations to unprecedented levels that opened up the era of non-linear XUV and x-ray optics. In this quest, laser driven high order harmonic generation sources providing attosecond resolution in the XUV spectral region enabled XUV-pump-XUV-pr...

The quantum mechanical motion of electrons and nuclei in systems spatially confined to the molecular dimensions occurs on the sub-femtosecond to the femtosecond timescales respectively. Consequently, the study of ultrafast electronic and, in specific cases, nuclear dynamics requires the availability of light pulses with attosecond (asec) duration a...

High-harmonic generation (HHG) in crystals offers a simple, affordable and easily accessible route to carrier-envelope phase (CEP) measurements, which scales favorably towards longer wavelengths. We present measurements of HHG in ZnO using few-cycle pulses at 3.1µm. Thanks to the broad bandwidth of the driving laser pulses, spectral overlap between...

Nonclassical light sources have a vital role in quantum optics as they offer a unique resource for studies in quantum technology. However, their applicability is restricted by their low intensity, while the development of new schemes producing intense nonclassical light is a challenging task. In this perspective article, we discuss potential scheme...

Motivated by the achieved high intensities of novel extreme ultraviolet (XUV) radiation sources, such as free electron lasers and laser-driven high harmonic generation beamlines, we elaborate on their perspective in inducing observable strong field effects. The feasibility of extending such effects from the infrared and visible spectral regimes in...

Electron quantum path interferences in strongly laser-driven aligned molecules and their dependence on the molecular alignment is an essential open problem in strong-field molecular physics. Here, we demonstrate an approach which provides direct access to the observation of these interference processes. The approach is based on the combination of t...

Attoscience is the emerging field that accesses the fastest electronic processes occurring at the atomic and molecular length scales with attosecond (1 as = 10^-18s) time resolution having wide ranging physical, chemical, material science and biological applications. The quintessential and one of the most fundamental processes in this domain is the...

The long-standing scientific quest of real-time tracing electronic motion and dynamics in all states of matter has been remarkably benefited by the development of intense laser-based pulsed sources with a temporal resolution in the attosecond [1 attosecond = 10⁻¹⁸ s] time scale. Nowadays, attosecond pulses are routinely produced in laboratories by...

We report the application of the time gated ion microscopy technique in accessing online the position of the source of harmonics generated in atomic gas media. This is achieved by mapping the spatial extreme-ultraviolet (XUV)-intensity distribution of the harmonic source onto a spatial ion distribution, produced in a separate focal volume of the ge...

Electrodynamical processes induced in complex systems like semiconductors by strong electromagnetic fields have traditionally been described using semiclassical approaches. Although these approaches allowed the investigation of ultrafast dynamics in solids culminating in multipetahertz electronics, they do not provide any access to the quantum-opti...

We report the application of the time gated ion microscopy technique in accessing online the position of the source of harmonics generated in atomic gas media. This is achieved by mapping the spatial extreme-ultraviolet (XUV)-intensity distribution of the harmonic source onto a spatial ion distribution, produced in a separate focal volume of the ge...

Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet and x-ray spectral ranges. Their practical realization, however, is still a challenging task and requires identification of optimum experimental conditions and parameters. Here, we present mea...

The present work reports on the generation of short-pulse coherent extreme ultraviolet radiation of controlled polarization. The proposed strategy is based on high-order harmonics generated in pre-aligned molecules. Field-free molecular alignment produced by a short linearly-polarized infrared laser pulse is used to break the isotropy of a gas medi...

We review the main research directions ongoing in the development of high-harmonic generation-based extreme ultraviolet sources for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniq...

Electrodynamical processes induced in complex systems like semiconductors by strong electromagnetic fields, have traditionally/conventionally been described using semi-classical approaches. Although these approaches, allowed the investigation of ultrafast dynamics in solids culminating in multi-petahertz electronics, they do not provide any access...

The study of core electron dynamics through nonlinear spectroscopy requires intense isolated attosecond extreme ultraviolet or even X-ray pulses. A robust way to produce these pulses is high-harmonic generation (HHG) in a gas medium. However, the energy upscaling of the process depends on a very demanding next-generation laser technology that provi...

We report the observation of multiple ionization of argon through multi-XUV-photon absorption induced by an unprecedentedly powerful laser driven high-order harmonic generation source. Comparing the measured intensity dependence of the yield of the different argon charge states with numerical calculations we can infer the different channels—direct...

Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet (XUV) and X-ray spectral range. However, its experimental realization is still a challenging task requiring identification of the optimum conditions for the generation of isolated attosecond p...

We report the observation of multiple ionization of Argon through multi-XUV-photon absorption induced by an unprecedentedly powerful laser driven high-harmonic-generation source. Comparing the measured intensity dependence of the yield of the different Argon charge states with numerical calculations we can infer the different channels -direct and s...

We demonstrate multiphoton ionization of inner-shell electrons in Xenon with 100-eV attosecond pulses. This was achieved with a novel XUV source based on high-harmonic generation in the gas phase driven with multi-TW few-cycle laser pulses.

Nonlinear light-matter interactions in the extreme ultraviolet (XUV) are a prerequisite to perform XUV-pump/XUVprobe spectroscopy of core electrons. Such interactions are now routinely investigated at free-electron laser (FEL) facilities. Yet, electron dynamics are often too fast to be captured with the femtosecond resolution of state-of-theart FEL...

Along with the review of the technological frame that will be available at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) we present considerations applicable to large-scale attosecond sources driven by high-power laser pulses.

We present conditions, based on loose focusing geometries, which can be used for the generation of ultrahigh power XUV pulses. Preliminary data regarding the approach’s feasibility will be presented.

During the last decades, systematic efforts in ultra-short pulse generation led to the development of table-top sources with the capability of producing such pulses in the extreme-ultraviolet spectral range (XUV). Such pulses have been extensively exploited in the investigation of ultrafast dynamics in all states of matter. Intense XUV radiation, t...

The development of ultra-short intense laser sources in the visible and extreme ultraviolet (XUV) spectral range led to fascinating studies in laser-matter interactions and attosecond science. In the majority of these studies the system under investigation interacts with a focused light beam, which ionizes the system. The ionization products are us...

The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric s...

This review presents the technological infrastructure that will be available at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) international facility. ELI-ALPS will offer to the international scientific community ultrashort pulses in the femtosecond and attosecond domain for time-resolved investigations with unprecedented...

High-order harmonics in the extreme-ultraviolet spectral range, resulting from the strong-field laser-atom interaction, have been used in a broad range of fascinating applications in all states of matter. In the majority of these studies the harmonic generation process is described using semi-classical theories which treat the electromagnetic field...

Supplementary Figures, Supplementary Notes and Supplementary References.

Real-time observation of ultrafast dynamics in the microcosm is a fundamental approach for understanding the internal evolution of physical, chemical and biological systems. Tools for tracing such dynamics are flashes of light with duration comparable to or shorter than the characteristic evolution times of the system under investigation. While fem...