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Photoelectron Holographic Interferometry to Probe the Longitudinal Momentum Offset at the Tunnel Exit

Physical Review Letters 2019年第18期122卷 183202-183202页

作者： Min Li Hui Xie Wei Cao Siqiang Luo Jia Tan Yudi Feng Baojie Du Weiyu Zhang Yang Li Qingbin Zhang Pengfei Lan Yueming Zhou Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

Laser-induced electron tunneling underlies numerous emerging spectroscopic techniques to probe attosecond electron dynamics in atoms and molecules. The improvement of those techniques requires an accurate knowledge of the exit momentum for the tunneling wave packet. Here we demonstrate a photoelectron interferometric scheme to probe the electron momentum longitudinal to the tunnel direction at the tunnel exit by measuring the photoelectron holographic pattern in an orthogonally polarized two-color laser pulse. In this scheme, we use a perturbative 400-nm laser field to modulate the photoelectron holographic fringes generated by a strong 800-nm pulse. The fringe shift offers direct experimental access to the intermediate canonical momentum of the rescattering electron, allowing us to reconstruct the momentum offset at the tunnel exit with high accuracy. Our result unambiguously proves the existence of nonzero initial longitudinal momentum at the tunnel exit and provides fundamental insights into the nonquasistatic nature of the strong-field tunneling.

关键词： Atomic & molecular processes in external fields Multiphoton or tunneling ionization & excitation Ultrafast phenomena

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Asymmetry of the photoelectron momentum distribution from molecular ionization in elliptically polarized laser pulses

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Physical Review A 2019年第1期99卷 013431-013431页

作者： Ya-Nan Qin Min Li Yang Li Mingrui He Siqiang Luo Yali Liu Yueming Zhou Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

We theoretically study the photoelectron momentum distributions (PMDs) of H2+ in elliptically polarized laser fields by numerically solving the time-dependent Schrödinger equation. Depending on the internuclear distance of H2+, the PMDs reveal different asymmetries with respect to the major and minor axes of the laser ellipse. At an internuclear distance corresponding to the enhanced ionization region, the asymmetry of the PMDs is opposite to that of the companion atom. We attribute this phenomenon to the effect of the internal scattered electrons, which are mainly released at an earlier ionization moment with respect to the field maximum within each half cycle. We further show that the asymmetry of the PMDs in the elliptical laser fields can be used to identify the instant when the electron wave packet is released from the molecule.

关键词： Atomic & molecular processes in external fields Multiphoton or tunneling ionization & excitation Molecules Schroedinger equation Semiclassical methods

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Nonadiabaticity-induced ionization time shift in strong-field tunneling ionization

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Physical Review A 2019年第2期100卷 023414-023414页

作者： Wenhai Xie Min Li Siqiang Luo Mingrui He Kun Liu Qingbin Zhang Yueming Zhou Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

Laser-induced electron tunneling is one of the most fundamental strong-field phenomena. In laser-induced electron tunneling, it is usually assumed that the highest tunneling rate appears at the peak of the laser electric field corresponding to the shortest tunneling barrier. Here we show that this fundamental assumption is broken in an orthogonally polarized two-color laser field. We find that a rapid change of the instantaneous initial momentum at the tunnel exit can lead to a distinct ionization time shift between the instant of the maximum ionization rate and the peak of the electric-field strength. This ionization time shift can be either positive or negative depending on the degree of nonadiabaticity of the electron-tunneling process, and it is mapped to a measurable momentum shift in the photoelectron momentum distribution. These findings have significant implications for resolving attosecond electron dynamics and are essential to quantify possible tunneling delay time during strong-field ionization.

关键词： Atomic & molecular processes in external fields Multiphoton or tunneling ionization & excitation Ultrafast phenomena

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Orientation dependence of high-order harmonic generation in nanowire

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Physical Review A 2019年第3期99卷 033421-033421页

作者： Jiapeng Li Qingbin Zhang Liang Li Xiaosong Zhu Tengfei Huang Pengfei Lan Peixiang Lu School of Physics and Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

We investigate the orientation dependence of high-order harmonic generation (HHG) in nanowires by solving the time-dependent Schrödinger equation. It is found that the harmonic spectrum exhibits a two-plateau structure and the two plateaus have different orientation dependences. The harmonic yield of the first plateau reaches a maximum when the laser field is parallel to the nanowire and gets a strong suppression when the laser field is perpendicular to the nanowire. The harmonic yield of the second plateau increases first and reduces eventually with the change of the nanowire orientation. These phenomena can be explained by the time-dependent population imaging and the analysis of the transition probability between different energy bands. Our analysis shows a strong band-sensitive orientation dependence in low-dimensional material.

关键词： High-order harmonic generation Nonlinear optics Ultrafast optics

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Direct imaging of molecular rotation with high-order-harmonic generation

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Physical Review A 2019年第5期99卷 053419-053419页

作者： Yanqing He Lixin He Pengfei Lan Baoning Wang Liang Li Xiaosong Zhu Wei Cao Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

Direct imaging of molecular dynamics is a long-standing goal in physics and chemistry. As an emerging tool, high-order-harmonic spectroscopy (HHS) enables accessing molecular dynamics on femtosecond to attosecond time scales. However, decoding information from the harmonic signals is usually painstaking due to the coherent nature of high-order-harmonic generation (HHG). Here we show that this obstacle can be effectively overcome by exploiting machine learning in HHS. Combining the machine learning with an angle-resolved HHS method, the molecular movie with femtosecond resolution is reconstructed from the angular distributions of HHG measured at various time delays of the probe pulse. Such a movie distinctly shows the full information of the coherent rotational dynamics of molecules, which is unattained in previous studies. The experimental retrievals are in good agreement with the numerical simulations. Our findings provide a comprehensive picture of molecular rotation in space and time, which will facilitate the development of related research on molecular dynamics imaging.

关键词： Atomic & molecular processes in external fields

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Semiclassical analysis of photoelectron interference in a synthesized two-color laser pulse

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Physical Review A 2019年第6期100卷 063411-063411页

作者： Yudi Feng Min Li Siqiang Luo Kun Liu Baojie Du Yueming Zhou Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China

We measure the photoelectron energy spectra from strong-field ionization of Kr in a two-color laser pulse consisting of a strong 400-nm field and a weak 800-nm field. The intensities of the main above-threshold ionization (ATI) and sideband peaks in the photoelectron energy spectra oscillate roughly oppositely with respect to the relative phase between the two-color components. We study the photoelectron interferometry in the strong-field ATI regime from the view of interference of different electron trajectories in order to extend reconstruction of attosecond harmonic beating by interference of two-photon transitions (RABBITT)-type analysis to the strong-field regime. Based on the strong-field approximation model, we obtain analytical expressions for the oscillations of both ATI and sideband peaks with the relative phase. A phase shift of π/4 with respect to the field maximum of the two-color laser pulse is revealed for the interference maximum in the main ATI peak without including the effect of the atomic potential.

关键词： Atomic & molecular processes in external fields Multiphoton or tunneling ionization & excitation Ultrafast phenomena

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Erratum to “Luminance Learning for Remotely Sensed Image Enhancement Guided by Weighted Least Squares”

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IEEE Geoscience and Remote Sensing Letters 2022年 19卷

作者： Zhenghua Huang Zifan Zhu Qing An Zhicheng Wang Qin Zhou Tianxu Zhang Ali Saleh Alshomrani Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan China Artificial Intelligence School Wuchang University of Technology Wuhan China School of Electronics and Information Engineering Wuhan Donghu University Wuhan China Mathematical Modelling and Applied Computation Research Group (MMAC) King Abdulaziz University Jeddah Saudi Arabia

In the above article [1] , the model in (1) should be revised as \begin{equation*}\min _{\mathcal{I}^{\mathcal{B}}}\left\{\left(\mathcal{I}-\mathcal{I}^{\mathcal{B}}\right)^{2}+\lambda\left(a_{x}(\mathcal{I})\left(\frac{\partial \mathcal{I}^{\mathcal{B}}}{\partial x}\right)^{2}+a_{y}(\mathcal{I})\left(\frac{\partial \mathcal{I}^{\mathcal{B}}}{\partial y}\right)^{2}\right)\right\} \end{equation*} to be minimized for ${\mathcal {I}}^{\mathcal {B}}$ .

关键词： Remote sensing Image enhancement

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Continuous-wave frequency upconversion with a molecular optomechanical nanocavity

arXiv

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arXiv 2021年

作者： Chen, Wen Roelli, Philippe Hu, Huatian Verlekar, Sachin Amirtharaj, Sakthi Priya Barreda, Angela I. Kippenberg, Tobias J. Kovylina, Miroslavna Verhagen, Ewold Martínez, Alejandro Galland, Christophe LausanneCH-1015 Switzerland Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan430205 China Institute of Applied Physics Abbe Center of Photonics Friedrich Schiller University Jena Albert-Einstein-Str. 15 Jena07745 Germany Nanophotonics Technology Center Universitat Politècnica de València Camino de Vera s/n Valencia46022 Spain Center for Nanophotonics AMOLF Science Park 104 Amsterdam1098 XG Netherlands

Frequency upconversion is a cornerstone of electromagnetic signal processing, analysis and detection. It is used to transfer energy and information from one frequency domain to another where transmission, modulation or detection is technically easier or more efficient. Optomechanical transduction is emerging as a flexible approach to coherent frequency upconversion;it has been successfully demonstrated for conversion from radio- and microwaves (kHz to GHz) to optical fields. Nevertheless, optomechanical transduction of multi-THz and mid-infrared signals remains an open challenge. Here, we utilize molecular cavity optomechanics to demonstrate upconversion of sub-microwatt continuous-wave signals at ∼32 THz into the visible domain at ambient conditions. The device consists in a plasmonic nanocavity hosting a small number of molecules. The incoming field resonantly drives a collective molecular vibration, which imprints an optomechanical modulation on a visible pump laser and results in Stokes and anti-Stokes upconverted Raman sidebands with sub-natural linewidth, indicating a coherent process. The nanocavity offers 13 orders of magnitude enhancement of upconversion efficiency per molecule compared to free space, with a measured phonon-to-photon internal conversion efficiency larger than 10-4 per milliwatt of pump power. Our results establish a flexible paradigm for optomechanical frequency conversion using molecular oscillators coupled to plasmonic nanocavities, whose vibrational and electromagnetic properties can be tailored at will using chemical engineering and nanofabrication. Copyright © 2021, The Authors. All rights reserved.

关键词： Molecules

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Structuring Nonlinear Wavefront Emitted from Monolayer Transition-Metal Dichalcogenides

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Research 2020年第1期2020卷 1721-1730页

作者： Xuanmiao Hong Guangwei Hu Wenchao Zhao Kai Wang Shang Sun Rui Zhu Jing Wu Weiwei Liu Kian Ping Loh Andrew Thye Shen Wee Bing Wang Andrea Alù Cheng-Wei Qiu Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and TechnologyWuhan 430074China Department of Electrical and Computer Engineering National University of Singapore4 Engineering Drive 3Singapore 117583 Advanced Science Research Center City University of New YorkNew York 10031USA Department of Physics National University of Singapore2 Science Drive 3Singapore 117542 Institute of Materials Research and Engineering Agency for ScienceTechnology and Research2 Fusionopolis WayInnovis#08-03Singapore 138634 Department of Chemistry National University of Singapore3 Science Drive 3Singapore 17543 Centre for Advanced 2D Materials National University of SingaporeBlock S146 Science Drive 2Singapore 117546 Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205China

The growing demand for tailored nonlinearity calls for a structure with unusual phase discontinuity that allows the realization of nonlinear optical chirality,holographic imaging,and nonlinear wavefront ***-metal dichalcogenide(TMDC)monolayers offer giant optical nonlinearity within a few-angstrom thickness,but limitations in optical absorption and domain size impose restriction on wavefront control of nonlinear emissions using classical light *** contrast,noble metal-based plasmonic nanosieves support giant field enhancements and precise nonlinear phase control,with hundred-nanometer pixellevel resolution;however,they suffer from intrinsically weak nonlinear ***,we report a multifunctional nonlinear interface by integrating TMDC monolayers with plasmonic nanosieves,yielding drastically different nonlinear functionalities that cannot be accessed by either *** a hybrid nonlinear interface allows second-harmonic(SH)orbital angular momentum(OAM)generation,beam steering,versatile polarization control,and holograms,with an effective SH nonlinearityχ^((2))of~25 nm/*** designer platform synergizes the TMDC monolayer and plasmonic nanosieves to empower tunable geometric phases and large field enhancement,paving the way toward multifunctional and ultracompact nonlinear optical devices.

关键词： nonlinearity Transition yielding

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Cross-dimensional relaxation of Li7−Rb87 atomic gas mixtures in a spherical-quadrupole magnetic trap

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Physical Review A 2020年第1期101卷 012703-012703页

作者： Fang Fang Shun Wu Aaron Smull Joshua A. Isaacs Yimeng Wang Chris H. Greene Dan M. Stamper-Kurn Department of Physics University of California Berkeley California 94720 USA Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 China Department of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA Purdue Quantum Science and Engineering Institute Purdue University West Lafayette Indiana 47907 USA Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

We measure the interspecies interaction strength between Li7 and Rb87 atoms through cross-dimensional relaxation of two-element gas mixtures trapped in a spherical-quadrupole magnetic trap. We record the relaxation of an initial momentum-space anisotropy in a lithium gas when cotrapped with rubidium atoms, with both species in the |F=1,mF=−1〉 hyperfine state. Our measurements are calibrated by observing cross-dimensional relaxation of a Rb87-only trapped gas. Through Monte Carlo simulations, we compare the observed relaxation to that expected given the theoretically predicted energy-dependent differential cross section for Li7−Rb87 collisions. The experimentally observed relaxation occurs significantly faster than predicted theoretically, a deviation that appears incompatible with other experimental data characterizing the Li7−Rb87 molecular potential.

关键词： Atomic & molecular collisions Interatomic & molecular potentials Mixtures of atomic and/or molecular quantum gases Scattering of atoms, molecules, clusters & ions Scattering theory Ultracold collisions

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