Extreme ultraviolet (XUV) interferometry is technically challenging to implement. One approach to generating interference between two XUV pulses relies on driving high-harmonic generation in a gas jet with two collinearly overlapping infrared laser pulses. We investigate this scheme through a combined experimental and theoretical study, with particular emphasis on the regime of temporal overlap between the driving pulses. A special phase-modulation interferometry technique is implemented to increase the sensitivity for the comprehensive mapping of the strong-field induced high-order nonlinear response. We find that the dynamics arising from the interference of the two electric fields can be adequately described by the non-perturbative model developed by Lewenstein and co-workers.
We examine how the interference of a coherent light-pulse with its slightly time-delayed copy may generate a pulse nearly identical to the original one and ahead of it. The simplicity of this 2-pulse system enabled us to obtain exact analytic expressions of the pulse distortion, valid for a wide class of pulse shapes. Explicit results are given for the pulses usually considered (gaussian, hyperbolic secant) but also for more realistic pulses of strictly limited duration. We finally show that the efficiency of the 2-pulse system is comparable to that of the other superluminal systems, at least …
The development of multiplexing information transmission technology in the THz band may accelerate the arrival of the 6G era. In this paper, has demonstrated the feasibility of forming a sequence of subpulses in the temporal domain and the corresponding quasidiscrete spectrum in the THz frequency range. It is shown that despite the fact that the THz pulse has an exponential chirp, there is a "linkage relation" between spectrum and temporal structures of the THz pulse train. This fact can be used for encoding information in THz pulses for implementation in 6G communication systems in the future…
In this work the experimental realization of a tunable high photon flux extreme ultraviolet light source is presented. This is enabled by high harmonic generation of two temporally delayed driving pulses, resulting in a tuning range of 0.8 eV at the 19th harmonic at 22.8 eV. The implemented approach allows for fast tuning of the spectrum, is highly flexible and is scalable towards full spectral coverage at higher photon energies.
Delivering femtosecond laser light in the focal plane of a high numerical aperture microscope objective is still a challenge, despite significant developments in the generation of ultrashort pulses. One of the most popular techniques, used to correct phase distortions resulting from propagation through transparent media, is the multiphoton intrapulse interference phase scan (MIIPS). The accuracy of MIIPS however is limited when higher order phase distortions are present. Here we introduce an improvement, called Gated-MIIPS, which avoids shortcomings of MIIPS, reduces the influence of higher or…
We study the conditions for two-photon classical interference with coherent pulses. We find that the temporal overlap between optical pulses is not required for interference However, coherence within the same inputs is found to be essential for the interference.
Metallic gratings were fabricated using high energy laser interference lithography with a frequency tripled Nd:YAG nanosecond laser. The grating structures were first recorded in a photosensitive layer and afterwards transferred to an Au film. High quality Au gratings with a period of 770 nm and peak-to-valley heights of 20-60 nm exhibiting plasmonic resonance response were successfully designed, fabricated and characterized.
We model the build-up of inter-channel nonlinear interference noise (NLIN) in wavelength division multiplexed systems by considering the pulse collision dynamics in the time domain. The fundamental interactions can be classified as two-pulse, three-pulse, or four-pulse collisions and they can be either complete, or incomplete. Each type of collision is shown to have its unique signature and the overall nature of NLIN is determined by the relative importance of the various classes of pulse collisions in a given WDM system. The pulse-collision picture provides qualitative and quantitative insigh…
We studied the excitation process of silicon under an intense double pulse. We employed the three-temperature (electron, hole, and lattice) model (3TM) together with Maxwell's equations. We solved Maxwell's equations by the finite-difference time-domain approach. The lattice temperature and absorbed energy at the surface increase significantly when the two laser pulses overlap with constructive interference. On the other hand, destructive interference substantially reduces the efficiency of laser excitation. On average, the overlapped double pulse increases the efficiency to about twice the di…
Pulsed driving of Kerr microresonators represents a promising avenue for the efficient generation of soliton states associated with coherent optical frequency combs. The underlying physics has not, however, yet been comprehensively investigated. Here, we report on a numerical and theoretical study of the impact of de-synchronization between the periodic pump field and the train of solitons circulating in the cavity. We show that de-synchronization can affect the soliton configurations that can be sustained for given parameters, and that it can be leveraged to guarantee operation in the attract…
The double-slit interference in single-photon ionization of the diatomic molecular ion $\mathrm{H}_2^+$ is theoretically studied beyond the dipole approximation. Via simulating and comparing the interactions of the prealigned $\mathrm{H}_2^+$ and the hydrogen atom with the xuv pulses propagating in different directions, we illustrate two kinds of effects that are encoded in the interference patterns of the photoelectrons from $\mathrm{H}_2^+$: (i) the photon-momentum transfer and (ii) the finite speed of light. While both effects could modify the maxima of the interference fringes, we show tha…
We identify a novel regime of soliton-plasma interactions in which high-intensity ultrashort pulses of intermediate soliton order undergo coherent plasma-induced fission. Experimental results obtained in gas-filled hollow-core photonic crystal fibers are supported by rigorous numerical simulations. The cumulative blueshift of higher-order input solitons with ionizing intensities results in pulse splitting before the ultimate self-compression point, leading to the generation of robust pulse pairs with PHz bandwidths. The novel dynamics closes the gap between plasma-induced adiabatic soliton com…
We demonstrate experimentally a scheme to measure small temporal delays, much smaller than the pulse width, between optical pulses. Specifically, we observe an interference effect, based on the concepts of quantum weak measurements and weak value amplification, through which a sub-pulsewidth temporal delay between two femtosecond pulses induces a measurable shift of the central frequency of the pulse. The amount of frequency shift, and the accompanying losses of the measurement, can be tailored by post-selecting different states of polarization. Our scheme requires only spectrum measurements a…
We propose a new technique for comparing two Raman active samples. The method employs optical interference of the signals generated via coherent anti-Stokes Raman scattering (CARS) of broadband laser pulses with noisy spectra. It does not require spectrally resolved detection, and no prior knowledge about either the Raman spectrum of the samples, or the spectrum of the incident light is needed. We study the proposed method theoretically, and demonstrate it in a proof-of-principle experiment on Toluene and ortho-Xylene samples.
In this letter, we demonstrate the first all-fiber all-normal dispersion ytterbium-doped oscillator with nonlinear multimodal interference based saturable absorber capable to generate ultrashort dissipative soliton pulses. Additional to functioning as a saturable absorber, the use of multimode fiber segments between single mode fibers also ensures the bandpass filtering via multimode interference reimaging necessary to obtain dissipative soliton mode-locking. The oscillator generates dissipative soliton pulses at 1030 nm with 5.8 mW average power, 5 ps duration and 44.25 MHz repetition rate. P…
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 the pulse duration, peak intensity and instantaneous frequency is studied in a self-consistent manner based on Lewenstein formalism. Simulations involving macroscopic propagation effects are also considered. The study aims to reveal the microscopic b…
High harmonic generation in solids provides us compact and coherent UV sources. Our simulations illustrate abnormal harmonic yield dependence on the intensity of driving or pre-excitation pulses. A multielectron interference model is proposed to reveal the mechanism of the extreme nonlinear optical phenomena. We find that the $k$-resolved intraband harmonic demonstrates different symmetry, phase, and amplitude, which can be observed by using a resonant pre-excitation pulse. The position of the interference minimum obtained by solving the semiconductor Bloch equations agrees well with that obta…
Continuous-wave laser driven Kerr-nonlinear, optical microresonators have enabled a variety of novel applications and phenomena including the generation of optical frequency combs, ultra-low noise microwaves, as well as, ultra-short optical pulses. In this work we break with the paradigm of the continuous-wave optical drive and use instead periodic, pico-second optical pulses. We observe the deterministic generation of stable femtosecond dissipative cavity solitons on-top of the resonantly enhanced driving pulse. Surprisingly, the soliton pulse locks to the driving pulse enabling direct all-op…
The observation of the Hong-Ou-Mandel (HOM)-type two-photon interference (TPI) has played an important role in the development of photonic quantum technologies. The time-resolved coincidence-detection technique has been effectively used to identify and characterize the TPI phenomena of long-coherence optical fields. Here, we report on the experimental demonstration of the TPI of two phase-randomized weak coherent pulses with time-resolved coincidence detection. The mutual coherence time between the two weak coherent lights is determined by applying a frequency noise to one of the two interferi…
A scalable on-chip single-photon source at telecommunications wavelengths is an essential component of quantum communication networks. In this work, we numerically construct a pulse-regulated single-photon source based on an optical parametric amplifier in a nanocavity. Under the condition of pulsed excitation, we study the photon statistics of the source using the Monte Carlo wave-function method. The results show that there exits an optimum excitation pulse width for generating high-purity single photons, while the source brightness increases monotonically with increasing excitation pulse wi…
Femtosecond light pulses carrying optical angular momentums (OAMs), possessing intriguing properties of helical phase fronts and ultrafast temporal profiles, enable many applications in nonlinear optics, strong-field physics and laser micro-machining. While generation of OAM-carrying ultrafast pulses and their interactions with matters have been intensively studied in experiments, three-dimensional characterization of ultrafast OAM-carrying light beams in spatio-temporal domain has, however, proved difficult to achieve. Conventional measurement schemes rely on the use of a reference pulsed lig…
Unleashing HHG Efficiency: The Role of Driving Pulse Duration
Friedrich-Schiller-Universität Jena（耶拿弗里德里希·席勒大学）；Helmholtz-Institute Jena（耶拿赫尔姆霍兹研究所）；Fraunhofer Institute for Applied Optics and Precision Engineering（弗劳恩霍夫应用光学和精密工程研究所）
The carrier envelop phase (CEP) of isolated attosecond pulses (IAPs) is theoretically and experimentally investigated based on the assumption that a significant contribution originates from the measurable CEP jitter of the driving laser. By solving the timedependent Schrödinger equation, it is demonstrated that the attosecond CEP jitter of IAPs is minimized when the driving pulse is near its Fourier limit but with slightly negative chirp. Although, at present the utilization of the CEP of IAPs has limited applications, understanding and characterization of the CEP jitter of IAPs is the first s…
Stochastic power fluctuation in a fiber optic system due to the interplay among dispersion, nonlinearity and partial coherence of the source is investigated. An analytical expression for the power fluctuation of a signal pulse due to its interference with an echo pulse generated due to the nonlinear interaction of signal pulses in a fiber optic system excited by a partially coherent source is obtained. The analytical results show that the mean nonlinear distortion decreases as the coherence time of the source reduces consistent with our numerical simulations.
Reradiation of a spatially non-uniform ultrashort electromagnetic pulse interacting with the linear chain of multielectron atoms is studied in the framework of sudden perturbation approximation. Angular distributions of the reradiation spectrum for arbitrary number of atoms are obtained. It is shown that interference effects for the photon radiation amplitudes lead to appearing of "diffraction" maximums. The obtained results can be extended to the case of two- and three-dimensional crystal lattices and atomic chains. The approach developed allows also to take into account thermal vibrations of…
We investigate the liberation of an atomic electron by a linearly polarized single-cycle near-infrared laser pulse having a peak intensity that ensures tunneling. Based on phase space analysis and energy distribution in the instantaneous potential, we reveal the importance of quantum interference between tunneling and over-the-barrier pathways of escape. Tunneling is blurred both in space and time, and the contribution of tunneling at the mean energy is almost negligible. We suggest and justify improved initial conditions for a classical particle approximation of strong-field ionization, based…
A two-level medium, described by the Maxwell-Bloch (MB) system, is engraved by establishing a standing cavity wave with a linearly polarized electromagnetic field that drives the medium on both ends. A light pulse, polarized along the other direction, then scatters the medium and couples to the cavity standing wave by means of the population inversion density variations. We demonstrate that control of the applied amplitudes of the grating field allows to stop the light pulse and to make it move backward (eventually to drive it freely). A simplified limit model of the MB system with variable bo…
We analyze two-center interference effects in the yields of ionization of a dissociating hydrogen molecular ion by an ultrashort VUV laser pulse. To this end, we performed numerical simulations of the time-dependent Schrödinger equation for a H$_2^+$ model ion interacting with two time-delayed laser pulses. The scenario considered corresponds to a pump-probe scheme, in which the first (pump) pulse excites the molecular ion to the first excited dissociative state and the second (probe) pulse ionizes the electron as the ion dissociates. The results of our numerical simulations for the ionization…
High-index dielectric metasurfaces featuring Mie-type electric and magnetic resonances have been of a great interest in a variety of applications such as imaging, sensing, photovoltaics and others, which led to the necessity of an efficient large-scale fabrication technique. To address this, here we demonstrate the use of single-pulse laser interference for direct patterning of an amorphous silicon film into an array of Mie resonators. The proposed technique is based on laser-interference-induced dewetting. A precise control of the laser pulse energy enables the fabrication of ordered dielectr…
The effect of the pulse envelope on electron-positron pair creation in a circularly-polarised laser pulse is investigated. Interference on the length scale of the pulse envelope, and smoothness of the pulse edges are found to influence the pair spectrum. A toy model of a flat-top pulse is used to identify pulse envelope effects inaccessible to local approaches. Broadening of channel openings and a widening of the energy and transverse momentum distribution of the pair are found to receive contributions that are below the local harmonic threshold. By comparing pair yields in a flat-top, sine-sq…
We investigate how the quantum control of a two-level system (TLS) coupled to photons can modify and tune the TLS's photon absorption spectrum. Tuning and controlling the emission and the absorption is of much interest e.g.\ for the development of efficient interfaces between stationary and flying qubits in modern architectures for quantum computation and quantum communication. We consider the periodic pulse control, where the TLS is subjected to a periodic sequence of the near-resonant Rabi driving pulses, each pulse implementing a 180$^\circ$ rotation. For small inter-pulse delays, the absor…
We theoretically study the scaling with the driving wavelength of the high-order harmonic generation (HHG) under the simultaneous irradiation of an extreme ultraviolet (XUV) pulse. Surprisingly, when the cutoff energy and ionization yield are fixed, the harmonic yield is nearly independent of the driving wavelength. We identify its origin as the combination of the initial spatial width of the states excited by the XUV pulse, making the wavepacket spreading less prominent, and the shallowing of the ionization potential, which suggests complex nature of the wavelength dependence of HHG.
Multiphoton interference is an important phenomenon in modern quantum mechanics and experimental quantum optics, and it is fundamental for the development of quantum information science and technologies. Over the last three decades, several theoretical and experimental studies have been performed to understand the essential principles underlying such interference and to explore potential applications. Recently, the two-photon interference (TPI) of phase-randomized weak coherent states has played a key role in the realization of long-distance quantum communication based on the use of classical …
Single-photon sources are at the heart of quantum-optical networks, with their uniquely quantum emission and phenomenon of two-photon interference allowing for the generation and transfer of nonclassical states. Although a few analytical methods have been briefly investigated for describing pulsed single-photon sources, these methods apply only to either perfectly ideal or at least extremely idealized sources. Here, we present the first complete picture of pulsed single-photon sources by elaborating how to numerically and fully characterize non-ideal single-photon sources operating in a pulsed…
We study ultrafast ionization dynamics using orthogonally polarized two-color (OTC) laser pulses involving the resonant "first plus second" ($ω+2ω$) scheme. The scheme is illustrated by numerical simulations of the time-dependent Schrödinger equation and recording the photoelectron momentum distribution. On the basis of the simulations of this resonant ionization, we identify signatures of the dynamic Autler-Townes effect and dynamic interference, in which their characterization is not possible in spectral domain. Taking advantage of the OTC scheme we show that these dynamical effects, which o…
The generation of stable short optical pulses in mode-locked lasers is of tremendous importance for many applications. Mode-locking is a broad concept that encompasses different processes enabling short pulse formation. It typically requires an intracavity mechanism that discriminates between single and collective mode lasing, which can be complex and sometimes adds noise. Moreover, known mode-locking schemes do not guarantee phase stability of the carrier wave. Here we theoretically propose that injecting a detuned signal seamlessly leads to mode-locking in fiber lasers. We show that phase-lo…
Multimode fibers are widely explored for optical communication, imaging and sensing applications. The interference of fiber guided modes generates a speckle pattern, which has been used for high-precision spectroscopy, temperature, and strain sensing. Here we demonstrate a single-shot full-field temporal measurement technique based on a multimode fiber. The complex spatiotemporal speckle field is created by a reference pulse propagating through the fiber, and it interferes with a signal pulse. From the time-integrated interference pattern, both the amplitude and the phase of the signal are ret…
The smallest spot in optical lithography and microscopy is generally limited by diffraction. Quantum lithography, which utilizes interference between groups of N entangled photons, was recently proposed to beat the diffraction limit by a factor N. Here we propose a simple method to obtain N photons interference with classical pulses that excite a narrow multiphoton transition, thus shifting the "quantum weight" from the electromagnetic field to the lithographic material. We show how a practical complete lithographic scheme can be developed and demonstrate the underlying principles experimental…
