Soliton fusion is a fascinating and delicate phenomenon that manifests itself in optical fibers in case of interaction between co-propagating solitons with small temporal and wavelengths separation. The mechanism of g...Soliton fusion is a fascinating and delicate phenomenon that manifests itself in optical fibers in case of interaction between co-propagating solitons with small temporal and wavelengths separation. The mechanism of graduate acceleration of trailing soliton by dispersive waves radiated from the preceding one provides necessary conditions for soliton fusion at the advanced stage of supercontinuum generation in photonic crystal fibers. As a result large intensity robust light structures can propagate over significant distances. In the spectral domain fusion-like processes result in development of a new significant band at the long wavelength side of the spectrum.展开更多
Well established for the visible spectrum gaps of the transition metal dichalcogenide family,valleytronics—the control of valley charge and current by light—is comparatively unexplored for the THz gaps that characte...Well established for the visible spectrum gaps of the transition metal dichalcogenide family,valleytronics—the control of valley charge and current by light—is comparatively unexplored for the THz gaps that characterize graphene and topological insulators.Hereweshow that few cycle pulses of THz light can create and control a>90%valley polarized current in graphene,with lightwave control over the current magnitude and direction.This is underpinned by a light-matter symmetry breaking in the ultrafast limit of circularly polarized light,characterized by a symmetry lowering of the excited state charge distribution.Our findings both highlight the richness of few cycle light pulses in control over quantum matter,and provide a route towards a“THz valleytronics”in meV gapped systems.展开更多
X-ray scattering has been an indispensable tool in advancing our understanding of matter,from the first evidence of the crystal lattice to recent discoveries of nuclei’s fastest dynamics.In addition to the lattice,ul...X-ray scattering has been an indispensable tool in advancing our understanding of matter,from the first evidence of the crystal lattice to recent discoveries of nuclei’s fastest dynamics.In addition to the lattice,ultrafast resonant elastic scattering of soft X-rays provides a sensitive probe of charge,spin,and orbital order with unparalleled nanometre spatial and femto-to picosecond temporal resolution.However,the full potential of this technique remains largely unexploited due to its high demand on the X-ray source.Only a selected number of instruments at large-scale facilities can deliver the required short-pulsed and wavelength-tunable radiation,rendering laboratory-scale experiments elusive so far.Here,we demonstrate time-resolved X-ray scattering with spectroscopic contrast at a laboratory-based instrument using the soft-X-ray radiation emitted from a laser-driven plasma source.Specifically,we investigate the photo-induced response of magnetic domains emerging in a ferrimagnetic FeGd heterostructure with 9 ps temporal resolution.The achieved sensitivity allows for tracking the reorganisation of the domain network on pico-to nanosecond time scales in great detail.This instrumental development and experimental demonstration break new ground for studying material dynamics in a wide range of laterally ordered systems in a flexible laboratory environment.展开更多
Activating transitions between internal states of physical systems has emerged as an appealing approach to create lattices and complex networks.In such a scheme,the internal states or modes of a physical system are re...Activating transitions between internal states of physical systems has emerged as an appealing approach to create lattices and complex networks.In such a scheme,the internal states or modes of a physical system are regarded as lattice sites or network nodes in an abstract space whose dimensionality may exceed the systems’apparent(geometric)dimensionality.This introduces the notion of synthetic dimensions,thus providing entirely novel pathways for fundamental research and applications.Here,we analytically show that the propagation of multiphoton states through multiport waveguide arrays gives rise to synthetic dimensions where a single waveguide system generates a multitude of synthetic lattices.Since these synthetic lattices exist in photon-number space,we introduce the concept of pseudo-energy and demonstrate its utility for studying multiphoton interference processes.Specifically,the spectrum of the associated pseudo-energy operator generates a unique ordering of the relevant states.Together with generalized pseudo-energy ladder operators,this allows for representing the dynamics of multiphoton states by way of pseudo-energy term diagrams that are associated with a synthetic atom.As a result,the pseudo-energy representation leads to concise analytical expressions for the eigensystem of N photons propagating through M nearest-neighbor coupled waveguides.In the regime where N≥2 and M≥3,nonlocal coupling in Fock space gives rise to hitherto unknown all-optical dark states that display intriguing nontrivial dynamics.展开更多
Exceptional points(EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, the corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted...Exceptional points(EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, the corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted tremendous attention due to their unusual properties, topological features, and an enhanced sensitivity that depends on the order of the EP, i.e., the number of degenerate eigenmodes. Yet, experimentally engineering higher-order EPs in classical or quantum domains remain an open challenge due to the stringent symmetry constraints that are required for the coalescence of multiple eigenmodes. Here, we analytically show that the number-resolved dynamics of a single, lossy waveguide beam splitter, excited by N indistinguishable photons and post-selected to the N-photon subspace, will exhibit an EP of order N+1. By using the well-established mapping between a beam splitter Hamiltonian and the perfect state transfer model in the photon-number space,we analytically obtain the time evolution of a general N-photon state and numerically simulate the system’s evolution in the post-selected manifold. Our results pave the way toward realizing robust, arbitrary-order EPs on demand in a single device.展开更多
We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural ...We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons,for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.展开更多
Single-shot coherent diffraction imaging of isolated nanosized particles has seen remarkable success in recent years,yielding in-situ measurements with ultra-high spatial and temporal resolution.The progress of high-r...Single-shot coherent diffraction imaging of isolated nanosized particles has seen remarkable success in recent years,yielding in-situ measurements with ultra-high spatial and temporal resolution.The progress of high-repetition-rate sources for intense X-ray pulses has further enabled recording datasets containing millions of diffraction images,which are needed for the structure determination of specimens with greater structural variety and dynamic experiments.The size of the datasets,however,represents a monumental problem for their analysis.Here,we present an automatized approach for finding semantic similarities in coherent diffraction images without relying on human expert labeling.By introducing the concept of projection learning,we extend self-supervised contrastive learning to the context of coherent diffraction imaging and achieve a dimensionality reduction producing semantically meaningful embeddings that align with physical intuition.The method yields substantial improvements compared to previous approaches,paving the way toward real-time and large-scale analysis of coherent diffraction experiments at X-ray free-electron lasers.展开更多
Conservation of parity plays a fundamental role in our understanding of various quantum processes.However,it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multi...Conservation of parity plays a fundamental role in our understanding of various quantum processes.However,it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multiphoton character and the large number of states involved.Here we report an effect of parity in strong-field Rydberg-state excitation(RSE)by comparing the RSE probabilities of the N_(2) molecule and its companion atom Ar,which has a similar ionization potential but opposite parity of its ground state.Experimentally,we observe an oscillatory structure as a function of intensity with a period of about 50 TW∕cm^(2) in the ratio between the RSE yields of the two species,which can be reproduced by simulations using the time-dependent Schrödinger equation(TDSE).We analyze a quantum-mechanical model,which allows for interference of electrons captured in different spatial regions of the Rydberg-state wave function.In the intensity-dependent RSE yield,it results in peaks with alternating heights with a spacing of 25 TW∕cm^(2) and at the same intensity for both species.However,due to the opposite parities of their ground states,pronounced RSE peaks in Ar correspond to less pronounced peaks in N_(2) and vice versa,which leads to the period of 50 TW∕cm^(2) in their ratio.Our work reveals a novel parity-related interference effect in the coherent-capture picture of the RSE process in intense laser fields.展开更多
Intense-laser-induced above-threshold ionization of a bound electron into continuum states with low energy is investigated in the context of the strong-field approximation that allows for one act of rescattering of th...Intense-laser-induced above-threshold ionization of a bound electron into continuum states with low energy is investigated in the context of the strong-field approximation that allows for one act of rescattering of the re- visiting electron. The quantum orbits for forward and backward scattering are evaluated and generalized to arbitrary scattering angles. The velocity map of the liberated electron exhibits the well-known low-energy structure as well as other features off the polarization axis.展开更多
Silicon-based light sources, including light-emitting diodes(LEDs) and laser diodes(LDs) for information transmission, are urgently needed for developing monolithic integrated silicon photonics. Silicon with erbium io...Silicon-based light sources, including light-emitting diodes(LEDs) and laser diodes(LDs) for information transmission, are urgently needed for developing monolithic integrated silicon photonics. Silicon with erbium ions(Er^(3+)) doped by ion implantation is considered a promising approach, but it suffers from an extremely low quantum efficiency. Here we report an electrically pumped superlinear emission at 1.54 μm from Er/O-doped silicon planar LEDs, which are produced by applying a new deep cooling process. Stimulated emission at room temperature is realized with a low threshold current of ~6 mA(~0.8 A∕cm^(2)). Time-resolved photoluminescence and photocurrent results have revealed the complex carrier transfer dynamics by relaxing electrons from the Si conduction band to the Er^(3+) ion. This picture differs from the frequently assumed energy transfer via electron–hole pair recombination of the silicon host. Moreover, the amplified emission from the LEDs is likely due to a quasi-continuous Er/O-related donor band created by the deep cooling technique. This work paves the way for fabricating superluminescent diodes or efficient LEDs at communication wavelengths based on rare-earth-doped silicon.展开更多
Luminescence constitutes a unique source of insight into hot carrier processes in metals,including those in plasmonic nanostructures used for sensing and energy applications.However,being weak in nature,metal luminesc...Luminescence constitutes a unique source of insight into hot carrier processes in metals,including those in plasmonic nanostructures used for sensing and energy applications.However,being weak in nature,metal luminescence remains poorly understood,its microscopic origin strongly debated,and its potential for unraveling nanoscale carrier dynamics largely unexploited.Here,we reveal quantum-mechanical effects in the luminescence emanating from thin monocrystalline gold flakes.Specifically,we present experimental evidence,supported by first-principles simulations,to demonstrate its photoluminescence origin(i.e.,radiative emission from electron/hole recombination)when exciting in the interband regime.Our model allows us to identify changes to the measured gold luminescence due to quantum-mechanical effects as the gold film thickness is reduced.Excitingly,such effects are observable in the luminescence signal from flakes up to 40 nm in thickness,associated with the out-of-plane discreteness of the electronic band structure near the Fermi level.We qualitatively reproduce the observations with first-principles modeling,thus establishing a unified description of luminescence in gold monocrystalline flakes and enabling its widespread application as a probe of carrier dynamics and light-matter interactions in this material.Our study paves the way for future explorations of hot carriers and charge-transfer dynamics in a multitude of material systems.展开更多
文摘Soliton fusion is a fascinating and delicate phenomenon that manifests itself in optical fibers in case of interaction between co-propagating solitons with small temporal and wavelengths separation. The mechanism of graduate acceleration of trailing soliton by dispersive waves radiated from the preceding one provides necessary conditions for soliton fusion at the advanced stage of supercontinuum generation in photonic crystal fibers. As a result large intensity robust light structures can propagate over significant distances. In the spectral domain fusion-like processes result in development of a new significant band at the long wavelength side of the spectrum.
基金funding through project-ID 328545488 TRR227(projects A04)Shallcrosswould like to thank DFG for funding through project-ID 522036409 SH 498/7-1+1 种基金Sharma and Shallcross would like to thank the Leibniz Professorin Program(SAW P118/2021)The authors acknowledge the North-German Supercomputing Alliance(HLRN)for providing HPC resources that have contributed to the research results reported in this paper.
文摘Well established for the visible spectrum gaps of the transition metal dichalcogenide family,valleytronics—the control of valley charge and current by light—is comparatively unexplored for the THz gaps that characterize graphene and topological insulators.Hereweshow that few cycle pulses of THz light can create and control a>90%valley polarized current in graphene,with lightwave control over the current magnitude and direction.This is underpinned by a light-matter symmetry breaking in the ultrafast limit of circularly polarized light,characterized by a symmetry lowering of the excited state charge distribution.Our findings both highlight the richness of few cycle light pulses in control over quantum matter,and provide a route towards a“THz valleytronics”in meV gapped systems.
基金funding from the Leibniz Association through the Leibniz Junior Research Group Grant No.J134/2022from the Deutsche Forschungsgemeinschaft(DFG)through TRR 227,Project No.A02.
文摘X-ray scattering has been an indispensable tool in advancing our understanding of matter,from the first evidence of the crystal lattice to recent discoveries of nuclei’s fastest dynamics.In addition to the lattice,ultrafast resonant elastic scattering of soft X-rays provides a sensitive probe of charge,spin,and orbital order with unparalleled nanometre spatial and femto-to picosecond temporal resolution.However,the full potential of this technique remains largely unexploited due to its high demand on the X-ray source.Only a selected number of instruments at large-scale facilities can deliver the required short-pulsed and wavelength-tunable radiation,rendering laboratory-scale experiments elusive so far.Here,we demonstrate time-resolved X-ray scattering with spectroscopic contrast at a laboratory-based instrument using the soft-X-ray radiation emitted from a laser-driven plasma source.Specifically,we investigate the photo-induced response of magnetic domains emerging in a ferrimagnetic FeGd heterostructure with 9 ps temporal resolution.The achieved sensitivity allows for tracking the reorganisation of the domain network on pico-to nanosecond time scales in great detail.This instrumental development and experimental demonstration break new ground for studying material dynamics in a wide range of laterally ordered systems in a flexible laboratory environment.
基金Deutsche Forschungsgemeinschaft(BU 1107/12-2,PE 2602/2-2)Consejo Nacional de Ciencia y Tecnología(CB-2016-01/284372)+1 种基金Dirección General de Asuntos del Personal AcadémicoUniversidad Nacional Autónoma de México(UNAM-PAPIIT IN102920)。
文摘Activating transitions between internal states of physical systems has emerged as an appealing approach to create lattices and complex networks.In such a scheme,the internal states or modes of a physical system are regarded as lattice sites or network nodes in an abstract space whose dimensionality may exceed the systems’apparent(geometric)dimensionality.This introduces the notion of synthetic dimensions,thus providing entirely novel pathways for fundamental research and applications.Here,we analytically show that the propagation of multiphoton states through multiport waveguide arrays gives rise to synthetic dimensions where a single waveguide system generates a multitude of synthetic lattices.Since these synthetic lattices exist in photon-number space,we introduce the concept of pseudo-energy and demonstrate its utility for studying multiphoton interference processes.Specifically,the spectrum of the associated pseudo-energy operator generates a unique ordering of the relevant states.Together with generalized pseudo-energy ladder operators,this allows for representing the dynamics of multiphoton states by way of pseudo-energy term diagrams that are associated with a synthetic atom.As a result,the pseudo-energy representation leads to concise analytical expressions for the eigensystem of N photons propagating through M nearest-neighbor coupled waveguides.In the regime where N≥2 and M≥3,nonlocal coupling in Fock space gives rise to hitherto unknown all-optical dark states that display intriguing nontrivial dynamics.
基金Consejo Nacional de Ciencia y Tecnologia(CONACYT)(CB-2016-01/284372)National Science Foundation(NSF)(DMR-1054020)
文摘Exceptional points(EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, the corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted tremendous attention due to their unusual properties, topological features, and an enhanced sensitivity that depends on the order of the EP, i.e., the number of degenerate eigenmodes. Yet, experimentally engineering higher-order EPs in classical or quantum domains remain an open challenge due to the stringent symmetry constraints that are required for the coalescence of multiple eigenmodes. Here, we analytically show that the number-resolved dynamics of a single, lossy waveguide beam splitter, excited by N indistinguishable photons and post-selected to the N-photon subspace, will exhibit an EP of order N+1. By using the well-established mapping between a beam splitter Hamiltonian and the perfect state transfer model in the photon-number space,we analytically obtain the time evolution of a general N-photon state and numerically simulate the system’s evolution in the post-selected manifold. Our results pave the way toward realizing robust, arbitrary-order EPs on demand in a single device.
基金support of the Agence Nationale de la Recherche(projects ANR 2011 BS04010 NanoFlam and ANR 2011 BS09026 SmartLasir)
文摘We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons,for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.
文摘Single-shot coherent diffraction imaging of isolated nanosized particles has seen remarkable success in recent years,yielding in-situ measurements with ultra-high spatial and temporal resolution.The progress of high-repetition-rate sources for intense X-ray pulses has further enabled recording datasets containing millions of diffraction images,which are needed for the structure determination of specimens with greater structural variety and dynamic experiments.The size of the datasets,however,represents a monumental problem for their analysis.Here,we present an automatized approach for finding semantic similarities in coherent diffraction images without relying on human expert labeling.By introducing the concept of projection learning,we extend self-supervised contrastive learning to the context of coherent diffraction imaging and achieve a dimensionality reduction producing semantically meaningful embeddings that align with physical intuition.The method yields substantial improvements compared to previous approaches,paving the way toward real-time and large-scale analysis of coherent diffraction experiments at X-ray free-electron lasers.
基金National Key Research and Development Program of China(2019YFA0307700)National Natural Science Foundation of China(12174148,12074144,12074239)+1 种基金Li Ka Shing Foundation STU-GTIIT Joint Research(2024LKSFG02)STU Scientific Research Initiation(NTF23036T).
文摘Conservation of parity plays a fundamental role in our understanding of various quantum processes.However,it is difficult to observe in atomic and molecular processes induced by a strong laser field due to their multiphoton character and the large number of states involved.Here we report an effect of parity in strong-field Rydberg-state excitation(RSE)by comparing the RSE probabilities of the N_(2) molecule and its companion atom Ar,which has a similar ionization potential but opposite parity of its ground state.Experimentally,we observe an oscillatory structure as a function of intensity with a period of about 50 TW∕cm^(2) in the ratio between the RSE yields of the two species,which can be reproduced by simulations using the time-dependent Schrödinger equation(TDSE).We analyze a quantum-mechanical model,which allows for interference of electrons captured in different spatial regions of the Rydberg-state wave function.In the intensity-dependent RSE yield,it results in peaks with alternating heights with a spacing of 25 TW∕cm^(2) and at the same intensity for both species.However,due to the opposite parities of their ground states,pronounced RSE peaks in Ar correspond to less pronounced peaks in N_(2) and vice versa,which leads to the period of 50 TW∕cm^(2) in their ratio.Our work reveals a novel parity-related interference effect in the coherent-capture picture of the RSE process in intense laser fields.
文摘Intense-laser-induced above-threshold ionization of a bound electron into continuum states with low energy is investigated in the context of the strong-field approximation that allows for one act of rescattering of the re- visiting electron. The quantum orbits for forward and backward scattering are evaluated and generalized to arbitrary scattering angles. The velocity map of the liberated electron exhibits the well-known low-energy structure as well as other features off the polarization axis.
基金National Natural Science Foundation of China(61790583,61874043,61874072,21703140)Special-key project of the“Innovative Research Plan”+1 种基金Shanghai Municipality Bureau of Education(2019-01-07-00-02-E00075)Aero-Science Fund(201824X001)。
文摘Silicon-based light sources, including light-emitting diodes(LEDs) and laser diodes(LDs) for information transmission, are urgently needed for developing monolithic integrated silicon photonics. Silicon with erbium ions(Er^(3+)) doped by ion implantation is considered a promising approach, but it suffers from an extremely low quantum efficiency. Here we report an electrically pumped superlinear emission at 1.54 μm from Er/O-doped silicon planar LEDs, which are produced by applying a new deep cooling process. Stimulated emission at room temperature is realized with a low threshold current of ~6 mA(~0.8 A∕cm^(2)). Time-resolved photoluminescence and photocurrent results have revealed the complex carrier transfer dynamics by relaxing electrons from the Si conduction band to the Er^(3+) ion. This picture differs from the frequently assumed energy transfer via electron–hole pair recombination of the silicon host. Moreover, the amplified emission from the LEDs is likely due to a quasi-continuous Er/O-related donor band created by the deep cooling technique. This work paves the way for fabricating superluminescent diodes or efficient LEDs at communication wavelengths based on rare-earth-doped silicon.
基金ARB and FK acknowledge the support of SNSF Eccellenza Grant PCEGP2-194181ARB acknowledges SNSF Swiss Postdoctoral Fellowship TMPFP2_217040 and thanks Valeria Vento and Christophe Galland for the use of a commercial monocrystalline 200 nm gold sample,and Franky Esteban Bedoya Lora for the use of the Ocean Optics spectrometer.+5 种基金ARE,FI and FJGA acknowledge funding from the European Research Council(Advanced Grant No.789104-eNANO)the Spanish MICINN(PID2020-112625 GB-I00 and Severo Ochoa CEX2019-000910-S)the Catalan CERCA Program,and Fundacios Cellex and Mir-Puig.JDC is a Sapere Aude research leader supported by VILLUM FONDEN(Grant no.16498)Independent Research Fund Denmark(Grant no.0165-00051B)The Center for Polariton-driven Light-Matter Interactions(POLIMA)is funded by the Danish National Research Foundation(Project No.DNRF165)First-principles calculations were carried out at the Center for Computational Innovations at Rensselaer Polytechnic Institute.
文摘Luminescence constitutes a unique source of insight into hot carrier processes in metals,including those in plasmonic nanostructures used for sensing and energy applications.However,being weak in nature,metal luminescence remains poorly understood,its microscopic origin strongly debated,and its potential for unraveling nanoscale carrier dynamics largely unexploited.Here,we reveal quantum-mechanical effects in the luminescence emanating from thin monocrystalline gold flakes.Specifically,we present experimental evidence,supported by first-principles simulations,to demonstrate its photoluminescence origin(i.e.,radiative emission from electron/hole recombination)when exciting in the interband regime.Our model allows us to identify changes to the measured gold luminescence due to quantum-mechanical effects as the gold film thickness is reduced.Excitingly,such effects are observable in the luminescence signal from flakes up to 40 nm in thickness,associated with the out-of-plane discreteness of the electronic band structure near the Fermi level.We qualitatively reproduce the observations with first-principles modeling,thus establishing a unified description of luminescence in gold monocrystalline flakes and enabling its widespread application as a probe of carrier dynamics and light-matter interactions in this material.Our study paves the way for future explorations of hot carriers and charge-transfer dynamics in a multitude of material systems.
