Hui Li

Hui Li
East China Normal University | ECNU · State Key Laboratory of Precision Spectroscopy

Dr. rer. nat.

About

78
Publications
16,530
Reads
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1,428
Citations
Additional affiliations
September 2016 - present
East China Normal University
Position
  • Professor (Associate)
Description
  • ultrafast optics, atomic and molecular physics, nanophotonics, polaritonics
Education
August 2013 - July 2016

Publications

Publications (78)
Article
Full-text available
Exciton polaritons—quasi-particle excitations consisting of strongly coupled photons and excitons—present fascinating possibilities for photonic circuits, owing to their strong nonlinearity, ultrafast reaction times and their ability to form macroscopic quantum states at room temperature via non-equilibrium condensation. Past implementations of tra...
Article
Full-text available
In this study, we have explored the ultrafast formation and decay dynamics of exciton-polariton fluids at non-zero momenta, non-resonantly excited by a small-spot femtosecond pump pulse in a ZnO microcavity. Using the femtosecond angle-resolved spectroscopic imaging technique, multidimensional dynamics in both the energy and momentum degrees of fre...
Article
Full-text available
Nanoplasmas induced by intense laser fields have attracted enormous attention due to their accompanied spectacular physical phenomena which are vigorously expected by the community of science and industry. For instance, the energetic electrons and ions produced in laser-driven nanoplasmas are significant for the development of compact beam sources....
Article
Full-text available
Besides the diverse investigations on the interactions between intense laser fields and molecular systems, extensive research has been recently dedicated to exploring the response of nanosystems excited by well-tailored femtosecond laser fields. Due to the fact that nanostructures hold peculiar effects when illuminated by laser pulses, the underlyi...
Article
Full-text available
As compared to the intuitive process that the electron emits straight to the continuum from its parent ion, there is an alternative route that the electron may transfer to and be trapped by a neighboring ionic core before the eventual release. Here, we demonstrate that electron tunnelling via the neighboring atomic core is a pronounced process in l...
Article
We propose a method of generating and detecting spatially defined entanglement in exciton-polariton condensates at steady state. In our scheme we first create a spinor polariton condensate, such that steady-state squeezing is obtained under a one-axis twisting interaction. Then the condensate is split either physically or virtually, which results i...
Preprint
We propose a method of generating and detecting entanglement in two spatially separated excitonpolariton Bose-Einstein condensates (BECs) at steady-state. In our scheme we first create a spinor polariton BEC, such that steady-state squeezing is obtained under a one-axis twisting interaction. Then the condensate is split either physically or virtual...
Article
We report the ionization reduction of atoms in two-color femtosecond laser fields in this joint theoretical-experimental study. For the multiphoton ionization of atoms using a 400 nm laser pulse, the ionization probability is reduced if another relatively weak 800 nm laser pulse is overlapped. Such ionization reduction consistently occurs regardles...
Article
Full-text available
The near-field enhancement effect in nanoparticles dominates the dynamical response of the atoms and molecules within the nanosystem when interacting with ultrashort laser pulses. In this work, using the single-shot velocity map imaging technique, the angle-resolved momentum distributions of the ionization products from surface molecules in gold na...
Article
Parametric scattering dynamics are general and of crucial importance for cavity exciton polaritons. Here, parametric scattering process driven by exciton polariton condensates has been revealed in a 1D ZnO microcavity between the whispering-gallery mode and quasiwhispering-gallery mode. When the occupation of the produced polariton condensate is de...
Article
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Exciton polaritons have shown great potential for applications such as low-threshold lasing, quantum simulation, and dissipation-free circuits. In this paper, we realize a room temperature ultrafast polaritonic switch where the Bose-Einstein condensate population can be depleted at the hundred femtosecond timescale with high extinction ratios. This...
Article
By using the femtosecond angle-resolved spectroscopic imaging technique, the ultrafast buildup dynamics of room-temperature polariton condensation is explicitly visualized in a ZnO whispering gallery mode microcavity. The buildup time of polariton condensation with respect to the arrival of the femtosecond pump pulse decreases with the increasing p...
Article
Full-text available
By precisely controlling the waveform of ultrashort laser fields, electronic and nuclear motions in molecules can be steered on extremely short time scales, even in the attosecond regime. This new research field, termed "optochemistry", presents the light field in the time-frequency domain and opens new avenues for tailoring molecular reactions bey...
Article
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Rotational dynamics of D_{2} molecules inside helium nanodroplets is induced by a moderately intense femtosecond pump pulse and measured as a function of time by recording the yield of HeD^{+} ions, created through strong-field dissociative ionization with a delayed femtosecond probe pulse. The yield oscillates with a period of 185 fs, reflecting f...
Article
Full-text available
More than ten years ago, the observation of the low-energy structure in the photoelectron energy spectrum, regarded as an “ionization surprise,” has overthrown our understanding of strong-field physics. However, the similar low-energy nuclear fragment generation from dissociating molecules upon the photon energy absorption, one of the well-observed...
Article
Full-text available
Based on ZnO microcavities with high quality factors, where the gain medium exhibits confinement of wave packets due to the intrinsically formed whispering gallery microcavity, strong coupling between excitons and cavity photons can be obtained at room temperature resulting in hybrid quasiparticles, e.g. exciton polaritons. In this work, polariton...
Preprint
Full-text available
Rotational dynamics of D$_2$ molecules inside helium nanodroplets is induced by a moderately intense femtosecond (fs) pump pulse and measured as a function of time by recording the yield of HeD$^+$ ions, created through strong-field dissociative ionization with a delayed fs probe pulse. The yield oscillates with a period of 185 fs, reflecting field...
Article
Full-text available
In this work, by using femtosecond angle-resolved spectroscopic imaging technique, the ultrafast dynamics of confined exciton-polaritons in an optical induced potential well based on a ZnO whispering-gallery microcavity is explicitly visualized. The sub-picosecond transition between succeeding quantum harmonic oscillator states can be experimentall...
Article
Full-text available
Rather than being freed to the continuum, the strong-field tunneled electrons can make a trajectory driven by the remaining laser fields and have certain probability to be captured by the high lying Rydberg states of the parent atoms or molecules. To explore the effect of molecular orbital on Rydberg state excitation, the ellipticity dependence of...
Article
Full-text available
Using single-shot velocity map imaging technique, explosion imaging of different ion species ejected from 50 nm SiO 2 nanoparticles are obtained excitedly by strong near-infrared and ultraviolet femtosecond laser fields. Characteristic momentum distributions showing forward emission of the ions at low excitation intensities and shock wave behaviors...
Preprint
Whispering gallery modes in a microwire are characterized by a nearly equidistant energy spectrum. In the strong exciton-photon coupling regime, this system represents a bosonic cascade: a ladder of discrete energy levels that sustains stimulated transitions between neighboring steps. In this work, by using femtosecond angle-resolved spectroscopic...
Article
The dissociative above-threshold double ionization (ATDI) of H2 in strong laser fields involves the sequential releasing of two electrons at specific instants with the stretching of the molecular bond. By mapping the releasing instants of two electrons to their emission directions in a multicycle polarization-skewed femtosecond laser pulse, we expe...
Article
Full-text available
For a molecule irradiated by an intense laser field, the sudden excitation or removal of an electron will trigger ultrafast electronic and nuclear dynamics, of which the timescales are usually several orders different and can be separately treated according to the Born–Oppenheimer approximation. However, the electrons and nuclei are intrinsically c...
Article
Full-text available
We experimentally investigate the laser-induced dissociative frustrated multiple ionization of CO molecules; in this process one of the released electrons does not escape to the continuum but is eventually trapped into high-lying Rydberg states of the outgoing positively charged nuclear fragments at the ends of the laser pulse, leading to the forma...
Article
Full-text available
We experimentally investigate the dissociative frustrated double ionization of N2Ar dimers exposed to strong laser fields by measuring the ejected charged and excited neutral Rydberg fragments in coincidence. The results show that the tunneled electron is more likely to be recaptured by the argon atomic ion than the nitrogen molecular ion to form t...
Article
Full-text available
We investigate the longitudinal photon-momentum transfer in nonsequential double ionization of argon atoms exposed to a 2.0−μm linearly polarized strong laser field. The zero momentum of the photoelectron is precisely calibrated using the photoelectron-photoion coincidence spectrum. The sum-longitudinal momentum of two photoelectrons from the doubl...
Article
Full-text available
We experimentally investigate strong-field dissociative Rydberg excitation (DRE) of O2 molecules by using the photoelectron photoion coincidence spectrum, in which the outgoing neutral Rydberg fragments created by the strong laser fields are postionized by the weak static dc field of the spectrometer and afterwards detected as charged particles. Th...
Article
We experimentally observe the bond stretching time of one-photon and net-two-photon dissociation pathways of singly ionized H2 molecules driven by a polarization-skewed femtosecond laser pulse. By measuring the angular distributions of the ejected photoelectron and nuclear fragments in coincidence, the cycle-changing polarization of the laser field...
Article
Full-text available
We experimentally investigate Coulomb exploded directional double ionization of N 2 O molecules in elliptically polarized femtosecond laser pulses. The denitrogenation and deoxygenation channels are accessed via various pathways. It leads to distinct asymmetries in directional breaking of the doubly ionized N 2 O molecules versus the instantaneous...
Article
Full-text available
The photon-electron angular-momentum transfer is intrinsic and overwhelmingly important in light-molecule interaction. However, the photon-nuclei angular-momentum transfer is seldom observed because of the very large inertial moment and the very small dipole of nuclei as compared to those of the electron. Here, we report the theoretical and experim...
Article
Full-text available
Atoms and molecules exposed to strong laser fields can be excited to the Rydberg states with very high principal quantum numbers and large orbitals. It allows acceleration of neutral particles, generate near-threshold harmonics, and reveal multiphoton Rabi oscillations and rich photoelectron spectra. However, the physical mechanism of Rydberg state...
Article
Full-text available
The dissociative frustrated multiple ionization of hydrogen chloride (HCl) molecules in intense femtosecond laser fields is investigated by employing the coincidence measurement technique in cold target recoil ion momentum spectroscopy. Various dissociative frustrated multiple ionization channels caused by populating one or two electrons to highly...
Article
Full-text available
Theoretical studies indicated that C60 exposed to linearly polarized intense infrared pulses undergoes periodic cage structural distortions with typical periods around 100 fs (1 fs=10−15 s). Here, we use the laser-driven self-imaging electron diffraction technique, previously developed for atoms and small molecules, to measure laser-induced deforma...
Article
Full-text available
Orientation and alignment of molecules by ultrashort laser pulses is crucial for a variety of applications and has long been of interest in physics and chemistry, with the special emphasis on stereodynamics in chemical reactions and molecular orbitals imaging. As compared to the laser-induced molecular alignment, which has been extensively studied...
Article
Full-text available
An appealing property of optical diffractive structures from elastomeric materials is a possibility to regulate their optical patterns and consequently also their diffractive features with mechanical straining. We investigated the effect of strain on diffraction characteristics of holographic gratings recorded in a monodomain side-chain liquid crys...
Article
Full-text available
By measuring the ejected neutral and ionic fragments as well as the freed electron in coincidence, we track the laser induced dissociative frustrated double ionization (FDI) of D2, in which process one of the two tunneled electrons is eventually recaptured by the outgoing nuclei of the breaking molecule after the conclusion of the femtosecond laser...
Article
Full-text available
We experimentally investigate the dissociative double ionization of hydrogen chloride (HCl) molecules in intense femtosecond laser pulses. In addition to the prompt dissociation channels which occur on femtosecond timescales, long-lived hydrogen chloride dications which Coulomb-explode in flight towards the detector are clearly identified in the ph...
Article
Full-text available
Double ionization of nitrogen molecules in orthogonally polarized two-color femtosecond laser fields is investigated by varying the relative intensity between the fundamental wave (FW) and its second harmonic (SH) components. The yield ratios of the double ionization channels, i.e., the non-dissociative N2²⁺ and Coulomb exploded (N⁺, N⁺), to the si...
Preprint
Alignment and orientation of molecules by intense, ultrashort laser fields are crucial for a variety of applications in physics and chemistry. These include control of high harmonics generation, molecular orbitals tomography, control of molecular photoionization and dissociation processes, production of "molecular movies" with the help of X-ray fre...
Article
Full-text available
Significance Above-threshold ionization of atoms in strong laser fields is extensively studied for its overwhelming importance and universality. However, its counterpart, above-threshold dissociation of molecules in strong laser fields, is hard to be observed, although it has been predicted for decades. In this paper, by measuring the momenta of ph...
Article
Full-text available
We experimentally visualize the dissociative frustrated double ionization of hydrogen molecules by using few-cycle laser pulses in a pump-probe scheme, in which process the tunneling ionized electron is recaptured by one of the outgoing nuclei of the breaking molecule. Three internuclear distances are recognized to enhance the dissociative frustrat...
Article
Full-text available
By partially overlapping two time-delayed orthogonally polarized multicycle laser pulses of the same carrier frequency, we construct an optical waveform whose polarization axis rotates slowly for consecutive optical cycles. This unique laser field tunnel-ionizes atoms and accelerates the freed electrons to different directions at different instants...
Article
Full-text available
We experimentally investigate the single and double ionization of N2 and O2 molecules in bicircular two-color femtosecond laser pulses, and compare with their companion atoms of Ar and Xe with comparable ionization thresholds. Electron recollision assisted enhanced ionization is observed in N2 and Ar by controlling the helicity and field ratio betw...
Article
Full-text available
We experimentally investigate symmetric dissociative double ionization of acetylene in femtosecond laser pulses of various ellipticities. Two dissociative ionization pathways with kinetic energy release of 4.8 and 6.0 eV, denoted as the low- and high-EN pathways, are observed in the spectrum of the ejected fragment ions. The relative yield of the h...
Article
Full-text available
We report experimental observations of rotated echoes of alignment induced by a pair of time-delayed and polarization-skewed femtosecond laser pulses interacting with an ensemble of molecular rotors. Rotated fractional echoes, rotated high order echoes and rotated imaginary echoes are directly visualized by using the technique of coincident Coulomb...
Article
Full-text available
Being the simplest molecule on the planet, H2, as well as its isotopes, have been the prototype systems for strong-field molecular physics for decades. Photoionization and dissociation of H2 have been extensively investigated. After single ionization, the electron left in the molecular ion and its microscopic localization around the two dissociatin...
Article
Full-text available
The electron-nuclear joint energy spectrum allows one to unambiguously count the total number of photons absorbed by the electrons and nuclei of a molecule. Driven by phase-controlled, linearly polarized two-color femtosecond laser pulses, we experimentally demonstrate that the asymmetric bond breaking of a singly ionized H2 depends on the total nu...
Article
Full-text available
Directional breaking of the C-H/C-D molecular bond is manipulated in acetylene (C2H2) and deuterated acetylene (C2D2) by waveform controlled few-cycle mid-infrared laser pulses with a central wavelength around 1.6 μm at an intensity of about 8 × 10¹³ W/cm². The directionality of the deprotonation of acetylene is controlled by changing the carrier-e...
Article
Full-text available
The dissociative ionization of CO in orthogonally polarized femtosecond laser pulses are studied in a pump-probe scheme. The ionization of CO by the pump pulse and the dissociation of the created CO⁺ by the probe pulse can be fully disentangled by identifying the photoelectron momentum distributions. Different from the dissociative ionization by a...
Article
Full-text available
The transition between two distinct ionization mechanisms in femtosecond laser fields at 785 nm is observed for C60 molecules. The transition occurs in the investigated intensity range from 3-20 TW/cm² and is visualized in electron kinetic energy spectra below the one-photon energy (1.5 eV) obtained via velocity map imaging. Assignment of several o...
Preprint
Formation of high spatial frequency laser induced periodic surface structures (HSFL) in germanium by femtosecond mid-IR pulses with wavelengths between $\lambda=2.0$ and $3.6 \; \mathrm{\mu m}$ was studied with varying angle of incidence and polarization. The period of these structures varied from $\lambda/3$ to $\lambda/8$. A modified surface-scat...
Thesis
Full-text available
This thesis presents work on the interaction of waveform controlled few-cycle pulses with various systems, from simple diatomic molecules through hydrocarbons and C60 fullerene, to nano-sized silver clusters. By employing the single-shot phase-tagged velocity-map imaging (VMI) technique, the angular distributions of ionic fragmentations and electro...
Article
Full-text available
The dissociative ionization of toluene initiated by a few-cycle laser pulse as a function of the carrier envelope phase (CEP) is investigated using single-shot velocity map imaging. Several ionic fragments, CH3⁺, H2⁺, and H3⁺, originating from multiply charged toluene ions present a CEP-dependent directional emission. The formation of H2⁺ and H3⁺ i...
Article
Full-text available
We have studied the dissociative ionization of DCl in 4 fs laser fields at 720 nm central wavelength using intensities in the range (1.3?3.1)?×?1014 W cm?2. By employing the phase-tagged velocity-map imaging technique, information about the angular distribution of deuterium ions as a function of their kinetic energy and the carrier-envelope phase i...
Conference Paper
Laser-driven electron diffraction, which offers sub-cycle time resolution down to attoseconds, has so far only been demonstrated for small, diatomic molecules. We demonstrate the application of the technique to C60 showing its full potential.
Article
Full-text available
Proton migration is a ubiquitous process in chemical reactions related to biology, combustion, and catalysis. Thus, the ability to control the movement of nuclei with tailored light, within a hydrocarbon molecule holds promise for far-reaching applications. Here, we demonstrate the steering of hydrogen migration in simple hydrocarbons, namely acety...
Article
Full-text available
Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C_{60} fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailor...
Article
Full-text available
We follow the alignment-assisted orientation technique proposed by Zhang et al. [Phys. Rev. A 83, 043410 (2011)] to experimentally demonstrate a substantial enhancement of the field-free orientation by using a combination of single-and two-color laser pulses. When a two-color orienting pulse is preceded by a single-color aligning pulse by a suitabl...