A5041150434- Terahertz technology and applications
- Spectroscopy and Laser Applications
- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Gyrotron and Vacuum Electronics Research
- Topological Materials and Phenomena
- Laser-Plasma Interactions and Diagnostics
- Advanced Chemical Physics Studies
- Graphene research and applications
- Superconducting and THz Device Technology
- Orbital Angular Momentum in Optics
- Photonic and Optical Devices
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- Mass Spectrometry Techniques and Applications
- Laser Design and Applications
- Quantum many-body systems
- Cold Atom Physics and Bose-Einstein Condensates
- Photonic Crystal and Fiber Optics
- Plasmonic and Surface Plasmon Research
- Photorefractive and Nonlinear Optics
- Atmospheric Ozone and Climate
- Advanced Condensed Matter Physics
- Diamond and Carbon-based Materials Research
- Plant and animal studies
Chinese Academy of Sciences
2011-2024
University of Chinese Academy of Sciences
2020-2024
Shanghai Institute of Optics and Fine Mechanics
2013-2023
State Key Laboratory of High Field Laser Physics
2015
Northwestern University
2010-2013
Waveform-controlled terahertz (THz) radiation is of great importance due to its potential application in THz sensing and coherent control quantum systems. We demonstrated a novel scheme generate waveform-controlled from air plasma produced when carrier-envelope-phase (CEP) stabilized few-cycle laser pulses undergo filamentation ambient air. launched CEP-stabilized 10 fs-long (~1.7 optical cycles) at 1.8 μm into found that the generated waveform can be controlled by varying filament length...
A method for generating terahertz (THz) necklace beams from two-color vortex-laser-induced air plasma is proposed and theoretically investigated based on the frequency down-conversion process. The numerical demonstrations both four-wave mixing photocurrent schemes confirm that generated THz pulse a shear beam without orbital angular momentum (OAM), whose phase manifested as stepwise jump versus azimuthal angle. origin of OAM vanishing attributed to fact difference between field components...
We experimentally observe the bond stretching time of one-photon and net-two-photon dissociation pathways singly ionized ${\mathrm{H}}_{2}$ molecules driven by a polarization-skewed femtosecond laser pulse. By measuring angular distributions ejected photoelectron nuclear fragments in coincidence, cycle-changing polarization field enables us to clock photon-ionization starting photon-dissociation stopping time, analogous stopwatch. After single ionization ${\mathrm{H}}_{2}$, our results show...
We demonstrate the measurement of field-free molecular alignment air can be realized by combining weak field polarization technique (WFPT) with a balanced detection system. The measured signal is proportional to parameter. Periodic revival structures transient and permanent between revivals detected clearly single high sensitivity. Fourier transform spectrum agrees well calculation result provides information populations different J states in rotational wave packet.
Contribution of plasma oscillation to the broadband terahertz (THz) emission is revealed by interacting two-color (ω/2ω) laser pulses with a supersonic jet nitrogen molecules. Temporal and spectral shifts THz waves are observed as density varies. The former owes changing refractive index waves, latter correlates varying frequency. Simulation considering photocurrents, decaying explains spectrum spectrum. Plasma only contributes at low owing negligible absorption. At longer medium or higher...
The enhancement of even-order harmonics near the cut-off high-order harmonic spectra from monolayer MoS 2 has been experimentally observed recently by several groups. Here we demonstrate that this can be interpreted as a result spectral interference between half-cycles with opposite polarity adopting fully quantum mechanical calculation. We found that, due to energy modulation induced Berry connections, only same generate frequency, thus lack destructive leads enhanced intensity...
Optical vortices with longitudinal orbital angular momentum (OAM) as a powerful tool for particle control, imaging and communication have been greatly developed. We introduce novel property of broadband terahertz (THz) pulse, represented by frequency-dependent OAM orientation in spatiotemporal domain transverse projection. illustrate THz optical vortex (STOV) plasma-based emission driven cylindrical symmetry broken two-color field. detect the evolution time-delayed 2D electro-optic sampling...
We demonstrate the generation and control of elliptically polarized terahertz (THz) waves from air plasma produced by circularly few-cycle laser pulses. Experimental calculated results reveal that electric field asymmetry in rotating directions pulses produces enhanced broadband transient currents, phase difference perpendicular components is partially inherited process THz emission. The ellipticity emission its major axis direction are all-optically controlled duration carrier-envelope
A novel all-optical control scheme is proposed to continuously tune the THz radiation polarization, where driving laser based on a three-pulse configuration with adjustable time delays or intensity ratio. With this scheme, not only circularly polarized realized, continuous tuning from circular polarization linear can also be obtained conveniently just by adjusting Moreover, left right chirality of transformed between each other suitable delays.
Sub-optical-cycle electron dynamics in materials driven by intense laser fields can be investigated high harmonic generation. We observed frequency shift of spectrum near the band gap monolayer MoS2 experimentally. Through semi-classical quantum trajectory analysis, we demonstrated that phase transition dipole moment varies according to recombination timing and momentum tunneled electrons. It results either blue- or red-shift frequencies, determined modulated energy phases (TDPs) Berry...
We have observed the Berry phase effect associated with interband coherence in topological surface states (TSSs) using two-color high-harmonic spectroscopy. This accumulates along evolution path of strong field-driven electron-hole quasiparticles electronic bands spin-orbit coupling. By introducing a secondary weak field, we perturb Dirac fermions TSSs and thus provide access to phase. observe significant shift oscillation even-order harmonics from spectral interferogram. reveal that such...
We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that harmonics originate from multiple-step transitions among energy bands in momentum space, while odd-order are mainly direct transitions. The lower valence band is found vital even harmonics. Relative intensity versus odd orders calculated shows growing trend as laser field amplitude increases.
Three-dimensional topological insulators feature unconventional two-dimensional surface states, the carriers in which are helical Dirac fermions and protected from backscattering. Thus, they exhibit novel electronic response upon illuminate ultrashort intense laser light. We briefly reviewed recent studies on ultrafast phenomena of driven by pulse ranging visible to THz frequency. Ultrafast dynamics can be excited photons strong light field. Many unique nonlinear behaviors have been...
The evolution of THz waveform generated in air plasma provides a sensitive probe to the variation carrier envelope phase (CEP) propagating intense few-cycle pulses. Our experimental observation and calculation reveal that number positions inversion are dependent on initial CEP, which is near 0.5{\pi} constantly under varied input pulse energies when two inversions become one. This method measuring CEP an accuracy only limited by stability driving
We demonstrated a scheme to differentiate the high-harmonic generation (HHG) originating from surface states and bulk of topological insulator Bi2Se3. By adopting two-color mid-infrared laser fields on Bi2Se3, we found that nonlinear response sensitively depends relative phase driving fields. The even harmonics arise with clear signature, whose modulation period equals cycle second-harmonic (SHG) field. reveal weak SHG perturbs nontrivial dipole electron-hole pair in states, thus leads HHG....
We report on a systematic investigation of the dissociation dynamics ${{\mathrm{H}}_{2}}^{+}$ in intense laser fields, and study how kinetic energy spectrum dissociating proton can be modulated by wavelength intensity driving field. In experiment, ${\mathrm{H}}_{2}$ is dissociatively ionized an pulse with varying carrier wavelengths ranging from 800 to 1800 nm peak intensities. A model based Floquet theory Landau-Zener adopted explain experimental observations. The effect further explored...
We produce extremely bright mid-infrared (mid-IR) pulses with a tunable wavelength of 7 μm to 15 through difference frequency generation. Optimization beam quality and focusing results in an intense mid-IR field spatiotemporally confined the lambda-cubic volume. A near planar wavefront is achieved manipulating curvature pumping pulse downconversion process. Coherent are produced peak 280 MV/cm at 10 μm, its intensity exceeds 100 TW/cm2, estimated from measured energy, spatial temporal...
The self-focusing of few-cycle pulses at the wavelength 1800 nm under different focusing conditions and polarization states is experimentally investigated. critical power nonlinear refractive index for linearly circularly polarized are determined. value found much larger than that multi-cycle pulses, which consistent with previous result on 800 nm.
For many practical applications that need bright sources of mid-infrared radiation, single mode operation and good beam quality are also required. Quantum cascade lasers prominent candidates as compact radiation capable delivering very high power both CW under pulsed operation. While 1D photonic crystal distributed feedback structures can be used to get from quantum with narrow ridge widths, novel 2D cavity designs improve spectral spatial purity broad area lasers. In this paper, we...
We generate terahertz radiation in a supersonic jet of nitrogen molecules pumped by intense two-color laser pulses. The tuning spectra from blue shift to red is observed increasing power and stagnation pressure, the range enlarged with increased pressure. Our simulation reveals that plasma absorption oscillation currents expanded column owing intensity gas number density are crucial factors recurrence spectra. findings disclose microscopic mechanism present controlling knob for manipulation...
We demonstrate experimentally that in pump-probe experiment of H2 fragmentation by intense laser fields, the Coulomb explosion (CE) paths induced second ionization dissociating H2+ show varied dependencies on intensity. While charge resonance enhanced (CREI) channel is intensity dependent, probe CE (PICE) independent at certain delay time. By using a classical model, we calculated dissociation trajectories which agree well with experimental data.
The evolution of terahertz (THz) waveform in air plasma driven by low-energy few-cycle laser pulses is investigated to improve the accuracy carrier envelope phase (CEP) determination.Based on transient photocurrent model, a balanced spatial distribution Kerr and free-electron effects found at 109 µJ input energy.THz inversion occurs only once initial CEP 0.5π, which high-precision measurement achieved.