Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging o...Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging optics is not possible.However,current lensless imaging methods are typically limited by the need for a light source with a narrow,stable and accurately known spectrum.We have developed a general approach to lensless imaging without spectral bandwidth limitations or sample requirements.We use two time-delayed coherent light pulses and show that scanning the pulse-to-pulse time delay allows the reconstruction of diffraction-limited images for all the spectral components in the pulse.In addition,we introduce an iterative phase retrieval algorithm that uses these spectrally resolved Fresnel diffraction patterns to obtain high-resolution images of complex extended objects.We demonstrate this two-pulse imaging method with octave-spanning visible light sources,in both transmission and reflection geometries,and with broadband extreme-ultraviolet radiation from a high-harmonic generation source.Our approach enables effective use of low-flux ultra-broadband sources,such as table-top high-harmonic generation systems,for high-resolution imaging.展开更多
Supercontinuum white laser with large bandwidth and high pulse energy would offer incredible versatility and opportunities for basic science and high technology applications. Here, we report the generation of high-eff...Supercontinuum white laser with large bandwidth and high pulse energy would offer incredible versatility and opportunities for basic science and high technology applications. Here, we report the generation of high-efficiency 2.8-octave-spanning ultraviolet- visible-infrared (UV-Vis-IR) (with 350-2500 nm 25 dB bandwidth) supercontinuum white laser from a single chirped periodically poled lithium niobate (CPPLN) nonlinear crystal via synergic high-harmonic generation (HHG) and self-phase modulation (SPM). The CPPLN exhibits multiple controllable reciprocal-lattice bands to simultaneously support the quasi-phase matching (QPM) for simultaneous broadband 2nd-10th HHG via cascaded three-wave mixing against a broadband fundamental pump laser. Due to the efficient second-order nonlinearity (2nd-NL) up-conversion and significant 3rd-NL SPM effect both in the pump and HHG laser pulses, 350-2500 nm supercontinuum white laser is eventually obtained with 17 μJ per pulse under pump of 45 μJ per pulse mid-infrared femtosecond laser corresponding to an average high conversion efficiency of 37%. Our work opens up a route towards creating UV-Vis-IR all-spectrum white lasers through engineering the synergic action of HHG and SPM effects in nonlinear crystals for applications in ultrafast spectroscopy, single-shot remote sensing, biological imaging, and so on.展开更多
We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while ...We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while the odd-order harmonics are mainly from direct transitions. The lower valence band is found vital for the generation of even harmonics. Relative intensity of even-order harmonics versus the odd orders is calculated and shows a growing trend as the laser field amplitude increases.展开更多
We demonstrated a scheme to differentiate the high-harmonic generation[HHG)originating from the surface states and bulk states of the topological insulator Bi_(2)Se_(3).By adopting two-color mid-infrared laser fields ...We demonstrated a scheme to differentiate the high-harmonic generation[HHG)originating from the surface states and bulk states of the topological insulator Bi_(2)Se_(3).By adopting two-color mid-infrared laser fields on Bi_(2)Se_(3),we found that the nonlinear response sensitively depends on the relative phase of the driving fields.The even harmonics arise from the surface states with a clear signature,whose modulation period equals the cycle of the second-harmonic generation[SHG]field.We reveal that the weak SHG perturbs the nontrivial dipole phase of the electron-hole pair in surface states,and thus leads to the modulation of HHG.It provides a means to manipulate the ultrafast dynamics in surface states through adopting a weak perturbing laser field.展开更多
The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stab...The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stabiUzed laser pulses. Different patterns of harmonic spectra with varying CEP for the three interaction gas media are observed. Furthermore, in comparing our experiment results to the previous works driven by near-infrared laser pulses, different phenomena are found. Through numerical simulation, we find that for the two different kinds of driving fields, i.e. mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics.展开更多
We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation(SHHG)on plasma mirrors at a kilohertz repetition rate,emitted simultaneously with energetic electrons.SHHG ...We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation(SHHG)on plasma mirrors at a kilohertz repetition rate,emitted simultaneously with energetic electrons.SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length Lg for three increasingly short and intense driving pulses:24 fs and a0=1:1,8 fs and a0=1:6,and finally 4 fs and a0≈2:1,where a0 is the peak vector potential normalized by mec/e with the elementary charge e,the electron rest mass me,and the vacuum light velocity c.For all driver pulses,we observe correlated relativistic SHHG and electron emission in the range Lg∈½λ/20,λ/4,with an optimum gradient scale length of Lg≈λ/10.This universal optimal Lg-range is rationalized by deriving a direct intensity-independent link between the scale length Lg and an effective similarity parameter for relativistic laser-plasma interactions.展开更多
High-harmonic generation in metasurfaces,driven by strong laser fields,has been widely studied.Compared to plasma,all-dielectric nanoscale metasurfaces possess larger nonlinearity response and higher damage threshold....High-harmonic generation in metasurfaces,driven by strong laser fields,has been widely studied.Compared to plasma,all-dielectric nanoscale metasurfaces possess larger nonlinearity response and higher damage threshold.Additionally,it can strongly localize the driven field,greatly enhancing its peak amplitude.In this work,we adopt a Fano resonant micronano structure with transmission peaks at different wavelengths and explore its nonlinear response by both single and twocolor pump fields.Compared to the high-order harmonics induced by the first resonant wavelength,the intensity of the high-harmonic radiation results is enhanced by one order of magnitude,when the metasurface is driven by various resonant and non-resonant wavelength combinations of a two-color field.展开更多
‘Coherent control of high-harmonic generation in a two-color field’ has been widely concerned. Using split-operator algorithm, we have calculated the high-harmonic generation for helium ion He+ in a two-color field ...‘Coherent control of high-harmonic generation in a two-color field’ has been widely concerned. Using split-operator algorithm, we have calculated the high-harmonic generation for helium ion He+ in a two-color field which is composed of a driving field and a weak subsidiary high frequency field (Is = I0/100, (ω,13ω),...(ω, 120ω)) and found that such a field can produce much higher harmonic intensity, typically increasing the harmonics corresponding to the incident frequency of the subsidiary field. The different effects coming from the different subsidiary fields are calculated and analyzed. It is indicated that one of the important underlying mechanisms is high frequency photon induced radiation.展开更多
High harmonic generation(HHG)by two-color counter-rotating relativistic laser pulses with arbitrary frequency ratio is investigated through particle-in-cell simulations.It is shown that the dichromatic laser driver at...High harmonic generation(HHG)by two-color counter-rotating relativistic laser pulses with arbitrary frequency ratio is investigated through particle-in-cell simulations.It is shown that the dichromatic laser driver at various frequency ratios can effectively produce high-order harmonics with different spectral features.A general selection rule of this extended scheme can be obtained and the corresponding harmonic helicity can be identified through a simple analytical model based on a relativistic oscillating mirror.Thus,the results in this paper may offer new opportunities for arbitrary spectral control of generated harmonics,which is of significance for diverse potential applications in practice.展开更多
The high harmonic generation (HHG) from the CS<sub>2</sub> molecule in intense laser fields is investigated using the extended Lewenstein method. The initial state is the highest-occupied molecular orbital...The high harmonic generation (HHG) from the CS<sub>2</sub> molecule in intense laser fields is investigated using the extended Lewenstein method. The initial state is the highest-occupied molecular orbital of the CS<sub>2</sub> molecule, which can be well described by Gaussian wave packet using GAMESS-UK package. Compared with the case of the elliptical laser, the HHG can be extended in two-color circularly polarized laser field. The time-frequency analysis and classical electron trajectory as well as the ionization yield curve are also presented to further explain the underlying mechanism. After adding a static electric field on the z-direction, the single quantum path control is realized and the supercontinuum spectra are obtained. Moreover, an isolated 110 as pulse can be obtained by superposing the harmonics from 130th to 180th order.展开更多
基金This work is financed in part by an NWO-groot investment grant of the Netherlands Organisation for Scientific Research(NWO)and Laserlab Europe(JRA Bioptichal)SW acknowledges support from NWO Veni grant 680-47-402.
文摘Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging optics is not possible.However,current lensless imaging methods are typically limited by the need for a light source with a narrow,stable and accurately known spectrum.We have developed a general approach to lensless imaging without spectral bandwidth limitations or sample requirements.We use two time-delayed coherent light pulses and show that scanning the pulse-to-pulse time delay allows the reconstruction of diffraction-limited images for all the spectral components in the pulse.In addition,we introduce an iterative phase retrieval algorithm that uses these spectrally resolved Fresnel diffraction patterns to obtain high-resolution images of complex extended objects.We demonstrate this two-pulse imaging method with octave-spanning visible light sources,in both transmission and reflection geometries,and with broadband extreme-ultraviolet radiation from a high-harmonic generation source.Our approach enables effective use of low-flux ultra-broadband sources,such as table-top high-harmonic generation systems,for high-resolution imaging.
基金National Natural Science Foundation of China(11974119)Science and Technology Project of Guangdong(2020B010190001)+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2016ZT06C594)National Key R&D Program of China(2018YFA 0306200).
文摘Supercontinuum white laser with large bandwidth and high pulse energy would offer incredible versatility and opportunities for basic science and high technology applications. Here, we report the generation of high-efficiency 2.8-octave-spanning ultraviolet- visible-infrared (UV-Vis-IR) (with 350-2500 nm 25 dB bandwidth) supercontinuum white laser from a single chirped periodically poled lithium niobate (CPPLN) nonlinear crystal via synergic high-harmonic generation (HHG) and self-phase modulation (SPM). The CPPLN exhibits multiple controllable reciprocal-lattice bands to simultaneously support the quasi-phase matching (QPM) for simultaneous broadband 2nd-10th HHG via cascaded three-wave mixing against a broadband fundamental pump laser. Due to the efficient second-order nonlinearity (2nd-NL) up-conversion and significant 3rd-NL SPM effect both in the pump and HHG laser pulses, 350-2500 nm supercontinuum white laser is eventually obtained with 17 μJ per pulse under pump of 45 μJ per pulse mid-infrared femtosecond laser corresponding to an average high conversion efficiency of 37%. Our work opens up a route towards creating UV-Vis-IR all-spectrum white lasers through engineering the synergic action of HHG and SPM effects in nonlinear crystals for applications in ultrafast spectroscopy, single-shot remote sensing, biological imaging, and so on.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 11127901, 11134010, 61221064, and 61405222)the Strategic Priority Research Program of Chinese Academy of Sciences (CAS) (No. XDB16000000)。
文摘We present a velocity-gauge model for the generation of even-order high harmonics, and reveal that the even-order harmonics originate from the multiple-step transitions among the energy bands in momentum space, while the odd-order harmonics are mainly from direct transitions. The lower valence band is found vital for the generation of even harmonics. Relative intensity of even-order harmonics versus the odd orders is calculated and shows a growing trend as the laser field amplitude increases.
基金supported by the National Natural Science Foundation of China(Nos.12174412 and 11874373)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021241)+2 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20180023)the Natural Science Foundation of Henan Province(No.202300410017)the Xinxiang University Doctor Initial Research Program(No.1366020150).
文摘We demonstrated a scheme to differentiate the high-harmonic generation[HHG)originating from the surface states and bulk states of the topological insulator Bi_(2)Se_(3).By adopting two-color mid-infrared laser fields on Bi_(2)Se_(3),we found that the nonlinear response sensitively depends on the relative phase of the driving fields.The even harmonics arise from the surface states with a clear signature,whose modulation period equals the cycle of the second-harmonic generation[SHG]field.We reveal that the weak SHG perturbs the nontrivial dipole phase of the electron-hole pair in surface states,and thus leads to the modulation of HHG.It provides a means to manipulate the ultrafast dynamics in surface states through adopting a weak perturbing laser field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,61221064,11134010,11227902,11222439,and 11274325)the National Basic Research Program of China(Grant No.2011CB808103)the Funds from Shanghai Commission of Science and Technology(Grant No.12QA1403700)
文摘The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stabiUzed laser pulses. Different patterns of harmonic spectra with varying CEP for the three interaction gas media are observed. Furthermore, in comparing our experiment results to the previous works driven by near-infrared laser pulses, different phenomena are found. Through numerical simulation, we find that for the two different kinds of driving fields, i.e. mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics.
基金supported by the Agence Nationale pour la Recherche(ANR-11-EQPX-005-ATTOLAB and ANR-14-CE32-0011-03 APERO)Investissements d’Avenir Program LabEx PALM(ANR-10-LABX-0039-PALM)+2 种基金European Research Council(ERC FEMTOELEC 306708 and ERC ExCoMet 694596)Laserlab-Europe(H2020-EU.1.4.1.2.grant agreement ID 654148)Région Ile-de-France(SESAME 2012-ATTOLITE).
文摘We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation(SHHG)on plasma mirrors at a kilohertz repetition rate,emitted simultaneously with energetic electrons.SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length Lg for three increasingly short and intense driving pulses:24 fs and a0=1:1,8 fs and a0=1:6,and finally 4 fs and a0≈2:1,where a0 is the peak vector potential normalized by mec/e with the elementary charge e,the electron rest mass me,and the vacuum light velocity c.For all driver pulses,we observe correlated relativistic SHHG and electron emission in the range Lg∈½λ/20,λ/4,with an optimum gradient scale length of Lg≈λ/10.This universal optimal Lg-range is rationalized by deriving a direct intensity-independent link between the scale length Lg and an effective similarity parameter for relativistic laser-plasma interactions.
基金supported by the National Natural Science Foundation of China(Nos.11774215,91950101,and12074240)Sino-German Mobility Programme(No.M-0031)+2 种基金Department of Education of Guangdong Province(No.2018KCXTD011)High Level University Projects of Guangdong Province(Mathematics,Shantou University)Open Fund of the State Key Laboratory of High Field Laser Physics(SIOM)。
文摘High-harmonic generation in metasurfaces,driven by strong laser fields,has been widely studied.Compared to plasma,all-dielectric nanoscale metasurfaces possess larger nonlinearity response and higher damage threshold.Additionally,it can strongly localize the driven field,greatly enhancing its peak amplitude.In this work,we adopt a Fano resonant micronano structure with transmission peaks at different wavelengths and explore its nonlinear response by both single and twocolor pump fields.Compared to the high-order harmonics induced by the first resonant wavelength,the intensity of the high-harmonic radiation results is enhanced by one order of magnitude,when the metasurface is driven by various resonant and non-resonant wavelength combinations of a two-color field.
文摘‘Coherent control of high-harmonic generation in a two-color field’ has been widely concerned. Using split-operator algorithm, we have calculated the high-harmonic generation for helium ion He+ in a two-color field which is composed of a driving field and a weak subsidiary high frequency field (Is = I0/100, (ω,13ω),...(ω, 120ω)) and found that such a field can produce much higher harmonic intensity, typically increasing the harmonics corresponding to the incident frequency of the subsidiary field. The different effects coming from the different subsidiary fields are calculated and analyzed. It is indicated that one of the important underlying mechanisms is high frequency photon induced radiation.
基金supported by the National Key R&D Program of China(No.2018YFA0404802),Science Challenge Project(No.TZ2016005)National Natural Science Foundation of China(Nos.11774430,11875319)+3 种基金Research Project of NUDT(Nos.ZK18-02-02)Fok Ying-Tong Education Foundation(No.161007),the Fundamental Research Funds for the Central Universities(YJ202025)the Natural Science Foundation of Hunan Province(Nos.2020JJ5614 and 2020JJ5624)the Scientific Research Foundation of Hunan Provincial Education Department(No.20A042).
文摘High harmonic generation(HHG)by two-color counter-rotating relativistic laser pulses with arbitrary frequency ratio is investigated through particle-in-cell simulations.It is shown that the dichromatic laser driver at various frequency ratios can effectively produce high-order harmonics with different spectral features.A general selection rule of this extended scheme can be obtained and the corresponding harmonic helicity can be identified through a simple analytical model based on a relativistic oscillating mirror.Thus,the results in this paper may offer new opportunities for arbitrary spectral control of generated harmonics,which is of significance for diverse potential applications in practice.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11574117,11271158,61575077 and 11575071
文摘The high harmonic generation (HHG) from the CS<sub>2</sub> molecule in intense laser fields is investigated using the extended Lewenstein method. The initial state is the highest-occupied molecular orbital of the CS<sub>2</sub> molecule, which can be well described by Gaussian wave packet using GAMESS-UK package. Compared with the case of the elliptical laser, the HHG can be extended in two-color circularly polarized laser field. The time-frequency analysis and classical electron trajectory as well as the ionization yield curve are also presented to further explain the underlying mechanism. After adding a static electric field on the z-direction, the single quantum path control is realized and the supercontinuum spectra are obtained. Moreover, an isolated 110 as pulse can be obtained by superposing the harmonics from 130th to 180th order.
