Active control of terahertz(THz)waves is attracting tremendous attentions in terahertz communications and active photonic devices.Perovskite,due to its excellent photoelectric conversion performance and simple manufac...Active control of terahertz(THz)waves is attracting tremendous attentions in terahertz communications and active photonic devices.Perovskite,due to its excellent photoelectric conversion performance and simple manufacturing process,has emerged as a promising candidate for optoelectronic applications.However,the exploration of perovskites in optically controlled THz modulators is still limited.In this work,the photoelectric properties and carrier dynamics of FA_(0.4)MA_(0.6)PbI_(3)perovskite films were investigated by optical pumped terahertz probe(OPTP)system.The ultrafast carrier dynamics reveal that FA_(0.4)MA_(0.6)PbI_(3)thin film exhibits rapid switching and relaxation time within picosecond level,suggesting that FA_(0.4)MA_(0.6)PbI_(3)is an ideal candidate for active THz devices with ultrafast response.Furthermore,as a proof of concept,a FA_(0.4)MA_(0.6)PbI_(3)-based metadevice with integrating plasma-induced transparency(PIT)effect was fabricated to achieve ultrafast modulation of THz wave.The experimental results demonstrated that the switching time of FA_(0.4)MA_(0.6)PbI_(3)-based THz modulator is near to 3.5 ps,and the threshold of optical pump is as low as 12.7μJ cm^(-2).The simulation results attribute the mechanism of ultrafast THz modulation to photo-induced free carriers in the FA_(0.4)MA_(0.6)PbI_(3)layer,which progressively shorten the capacitive gap of PIT resonator.This study not only illuminates the potential of FA_(0.4)MA_(0.6)PbI_(3)in THz modulation,but also contributes to the field of ultrafast photonic devices.展开更多
The far-infrared optical properties of melamine and its deuterated isotope,melamine-d_6 were experimentally and theoretically investigated in the frequency range from 0.2 to 3.0 THz.Under the room temperature and dry ...The far-infrared optical properties of melamine and its deuterated isotope,melamine-d_6 were experimentally and theoretically investigated in the frequency range from 0.2 to 3.0 THz.Under the room temperature and dry air nitrogen conditions,three absorption bands were observed at 2.0,2.3 and 2.6 THz in the melamine sample by use of terahertz time-domain spectroscopy.Whereas,in the melamine-d_6 sample,the observed absorption bands shift towards lower frequencies and the relative intensity of the absorption bands reduces.Numerical simulation results based on the Parameterized Model number 3(PM3) were compared with the experimental data and the observed vibration spectra were assigned according to the PM3 calculations.The absorption bands of the measured melamine samples at terahertz frequencies are highly correlated with the intermolecular hydrogen bond stretching and π-π stacking vibration.Also,the red shift of the absorption bands is due to hydrogen/deuterium substitution.展开更多
We present a linear-cavity stretched-pulse fibre laser and by semiconductor saturable-absorber mirrors. A with mode locking by a nonlinear polarization rotation Q-switched mode-locking cw train and a mode-locking puls...We present a linear-cavity stretched-pulse fibre laser and by semiconductor saturable-absorber mirrors. A with mode locking by a nonlinear polarization rotation Q-switched mode-locking cw train and a mode-locking pulse train are obtained in the experiment. We investigate the effects of the equivalent fast saturable absorber and the slow saturable absorbers in experiment. It is found that neither the nonlinear polarization evolution effect nor a semiconductor saturable absorber mirror is enough to produce the stable cw mode-locking pulses in this experiment. A nonlinear polarization evolution effect controls the cavity loss to literally carve the pulses; semiconductor saturable absorber mirrors provide the self-restarting and maintain the stability of the modelocking operation.展开更多
We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong disper...We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong dispersive waves are simultaneously generated at 2.5μm and 4.6μm. It is deciphered that the interplay between plasma currents due to Kr ionization and nonlinear effects plays a key role in DW generation. Remarkably, this kind of DW generation is corroborated by the plasma-corrected phase-matching condition.展开更多
Based on the full-vector plane-wave method （FVPWM）, a hollow-core photonic crystal fibre （HC-PCF） fabricated by using the improved stack-and-draw technique is simulated. Under given propagation constants β, sever...Based on the full-vector plane-wave method （FVPWM）, a hollow-core photonic crystal fibre （HC-PCF） fabricated by using the improved stack-and-draw technique is simulated. Under given propagation constants β, several effective photonie band gaps with different sizes emerge within the visible wavelength range from 575 to 720 nm. The fundamental mode and second-order mode lying in a part of PBGs are investigated. In the transmission spectrum tested, the positions of PBGs are discovered to be shifting to shorter wavelengths. The main reason is the existence of interstitial holes at nodes in the cladding region. In the later experiment, green light is observed propagating in the air-core region, and the result is more consistent with our theoretical simulation.展开更多
For a typical photonic crystal fiber with two zero-dispersion wavelengths,we theoretically demonstrate a new way to generate supercontinuum using an input pulse of 30fs duration and lOkW peak power for providing a com...For a typical photonic crystal fiber with two zero-dispersion wavelengths,we theoretically demonstrate a new way to generate supercontinuum using an input pulse of 30fs duration and lOkW peak power for providing a compact and cost effective light source to the ultra-broadband time-resolved coherent anti-Stokes Raman scattering spectroscopy.展开更多
Metal-dielectric subwavelength gratings under s-polarized and p-polarized visible radiation are studied for discovering their intriguing behaviors of spectral resonance and color property.The dependence of their reson...Metal-dielectric subwavelength gratings under s-polarized and p-polarized visible radiation are studied for discovering their intriguing behaviors of spectral resonance and color property.The dependence of their resonance and color on grating parameters as well as angle of incidence and position of plane of incidence is also analyzed.For s-polarized light,the behavior of spectral resonance with single peak and higher peak efficiency is found.While transmission spectra for p-polarized light are not able to achieve a behavior like that of s-polarization,creating a perceived color is feasible.Moreover,a security grating with distinctive color shifts has been designed and its resonant properties as well as related color variation have also been provided.展开更多
We report a numerical investigation on terahertz wave propagation in plastic photonic band-gap fibres which are characterized by a 19-unit-cell air core and hexagonal Mr holes with rounded corners in cladding. Using t...We report a numerical investigation on terahertz wave propagation in plastic photonic band-gap fibres which are characterized by a 19-unit-cell air core and hexagonal Mr holes with rounded corners in cladding. Using the finite element method, the leakage loss and absorption loss are calculated and the transmission properties are analysed. The lowest loss of 0.268 dB/m is obtained. Numerical results show that the fibres could liberate the constraints of background materials beyond the transparency region in terahertz wave band, and efficiently minimize the effect of absorption by background materials, which present great advantage of plastic photonic band-gap fibres in long distance terahertz delivery.展开更多
Passively Q-switched quasi-continuous-wave （QCW） diode-pumped Nd：YAG laser with Cr^4＋ ：YAG as saturable absorber is numerically investigated by solving the coupled rate equations. The threshold pump rate for pass...Passively Q-switched quasi-continuous-wave （QCW） diode-pumped Nd：YAG laser with Cr^4＋ ：YAG as saturable absorber is numerically investigated by solving the coupled rate equations. The threshold pump rate for passively Q-switched QCW-pumped laser is derived. The effects of the pump rate and pump-pulse duration on the laser operation characteristics are studied theoretically. The pump power range can be estimated according to the number of output pulses. The numerical simulation results are in good agreement with the experimental results.展开更多
A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The charac...A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti：sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.展开更多
Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics ...Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics of plasmonic vortices,providing a better understanding of optical orbital angular momentums in the evanescent wave regime.However,these works only focused on the objective characterization of plasmonic vortex and have not achieved subjectively tailoring of its spatiotemporal dynamics for specific applications.Herein,it is demonstrated that the plasmonic vortices with the same topological charge can be endowed with distinct spatiotemporal dynamics by simply changing the coupler design.Based on a near-field scanning terahertz microscopy,the surface plasmon fields are directly obtained with ultrahigh spatiotemporal resolution,experimentally exhibiting the generation and evolution divergences during the whole lifetime of plasmonic vortices.The proposed strategy is straightforward and universal,which can be readily applied into visible or infrared frequencies,facilitating the development of plasmonic vortex related researches and applications.展开更多
We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrat...We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrate an unambiguous interference feature in the photoelectron spectra, and the interference is unveiled to originate from the dynamic Stark effect. The interference photoelectron spectra are prompted for intense sub-femtosecond XUV laser pulses in double ionization. The stationary phase picture is corroborated qualitatively in the two-electron system. The ability of probing the dynamic Stark effect by the photoelectron spectra in a pragmatic experiment of single-photon double ionization of He may shed light on further investigation on multi-electron atoms and molecules.展开更多
We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse...We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.展开更多
We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% a...We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.展开更多
A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an outpu...A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.展开更多
Wavelength modulation technique （WMT） and wavelength sweep technique （WST） are introduced into intra-cavity absorption gas sensors （ICAGS） for low concentration gas detection. The optimized parameters of the sys...Wavelength modulation technique （WMT） and wavelength sweep technique （WST） are introduced into intra-cavity absorption gas sensors （ICAGS） for low concentration gas detection. The optimized parameters of the system maximizing the signal-to-noise ratio （SNR） are found. Calibration of acetylene concentration and gas recognition are both realized.展开更多
This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the pola...This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the polarization of incident beam and crystal-orientation is discussed. For the experimental setup with a transceiver which transmits and detects terahertz radiation in the same crystal, we have demonstrated the optimal combination of both parameters above to optimize the working efficiency. Equations supplied in this paper are valid for zincblende crystals with arbitrary crystal- orientation and every possible polarization of an incident beam, which are of great significance for the optimization of a system.展开更多
A cw diode side-pumped Nd：YAO laser is frequency doubled to 532nm with an intracavity KTP crystal in a Vshaped arrangement, achieving an output power of 40 W corresponding to an optical-optical conversion efficiency ...A cw diode side-pumped Nd：YAO laser is frequency doubled to 532nm with an intracavity KTP crystal in a Vshaped arrangement, achieving an output power of 40 W corresponding to an optical-optical conversion efficiency of 9.7%. The instabilities and the M2-parameters of the laser are measured at different output powers after the beam is filtered.展开更多
Using a double resonant KTiOPO4 （KTP） intracavity optical parametric oscillator operating at degenerated point of 2 μm, we demonstrate a unique mid-infrared source based on difference frequency generation in GaSe c...Using a double resonant KTiOPO4 （KTP） intracavity optical parametric oscillator operating at degenerated point of 2 μm, we demonstrate a unique mid-infrared source based on difference frequency generation in GaSe crystal. The output tuning range is 8.42-19.52 μm, and a peak power of 834 W for type-Ⅰ phase matching scheme and 730 W for type-Ⅱ phase matching scheme are achieved. Experimental results show that this oscillator is a good alternative to the generator of a compact and tabletop mid-infrared radiation with a widely tunable range.展开更多
This paper numerically simulates the process of ablation of an aluminum target by an intense femtosecond laser with a fluence of 40 J/cm2 based on the two-temperature equation, and obtains the evolution of the free el...This paper numerically simulates the process of ablation of an aluminum target by an intense femtosecond laser with a fluence of 40 J/cm2 based on the two-temperature equation, and obtains the evolution of the free electron temperature and lattice temperature over a large temporal and depth range, for the first time. By investigating the temporal evolution curves of the free electron temperature and lattice temperature at three representative depths of 0, 100 nm and 500 nm, it reveals different characteristics and mechanisms of the free electron temperature evolution at different depths. The results show that, in the intense femtosecond laser ablation of aluminum, the material ablation is mainly induced by the thermal conduction of free electrons, instead of the direct absorption of the laser energy; in addition, the thermal conduction of free electrons and the coupling effect between electrons and lattice will induce the temperature of free electrons deep inside the target to experience a process from increase to decrease and finally to increase again.展开更多
基金supported by the National Natural Science Foundation of China(U1930117,12204445)。
文摘Active control of terahertz(THz)waves is attracting tremendous attentions in terahertz communications and active photonic devices.Perovskite,due to its excellent photoelectric conversion performance and simple manufacturing process,has emerged as a promising candidate for optoelectronic applications.However,the exploration of perovskites in optically controlled THz modulators is still limited.In this work,the photoelectric properties and carrier dynamics of FA_(0.4)MA_(0.6)PbI_(3)perovskite films were investigated by optical pumped terahertz probe(OPTP)system.The ultrafast carrier dynamics reveal that FA_(0.4)MA_(0.6)PbI_(3)thin film exhibits rapid switching and relaxation time within picosecond level,suggesting that FA_(0.4)MA_(0.6)PbI_(3)is an ideal candidate for active THz devices with ultrafast response.Furthermore,as a proof of concept,a FA_(0.4)MA_(0.6)PbI_(3)-based metadevice with integrating plasma-induced transparency(PIT)effect was fabricated to achieve ultrafast modulation of THz wave.The experimental results demonstrated that the switching time of FA_(0.4)MA_(0.6)PbI_(3)-based THz modulator is near to 3.5 ps,and the threshold of optical pump is as low as 12.7μJ cm^(-2).The simulation results attribute the mechanism of ultrafast THz modulation to photo-induced free carriers in the FA_(0.4)MA_(0.6)PbI_(3)layer,which progressively shorten the capacitive gap of PIT resonator.This study not only illuminates the potential of FA_(0.4)MA_(0.6)PbI_(3)in THz modulation,but also contributes to the field of ultrafast photonic devices.
基金supported by the Major Project of the National Natural Science Foundation of China (Grant Nos.60977064 and 61028011)Tianjin Sci-Tech Program(Grant No.07ZCGHHZ01100, Grant No.09ZCKFGX01500,and Grant No.10JCYB JC01400)
文摘The far-infrared optical properties of melamine and its deuterated isotope,melamine-d_6 were experimentally and theoretically investigated in the frequency range from 0.2 to 3.0 THz.Under the room temperature and dry air nitrogen conditions,three absorption bands were observed at 2.0,2.3 and 2.6 THz in the melamine sample by use of terahertz time-domain spectroscopy.Whereas,in the melamine-d_6 sample,the observed absorption bands shift towards lower frequencies and the relative intensity of the absorption bands reduces.Numerical simulation results based on the Parameterized Model number 3(PM3) were compared with the experimental data and the observed vibration spectra were assigned according to the PM3 calculations.The absorption bands of the measured melamine samples at terahertz frequencies are highly correlated with the intermolecular hydrogen bond stretching and π-π stacking vibration.Also,the red shift of the absorption bands is due to hydrogen/deuterium substitution.
文摘We present a linear-cavity stretched-pulse fibre laser and by semiconductor saturable-absorber mirrors. A with mode locking by a nonlinear polarization rotation Q-switched mode-locking cw train and a mode-locking pulse train are obtained in the experiment. We investigate the effects of the equivalent fast saturable absorber and the slow saturable absorbers in experiment. It is found that neither the nonlinear polarization evolution effect nor a semiconductor saturable absorber mirror is enough to produce the stable cw mode-locking pulses in this experiment. A nonlinear polarization evolution effect controls the cavity loss to literally carve the pulses; semiconductor saturable absorber mirrors provide the self-restarting and maintain the stability of the modelocking operation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11674243 and 11674242
文摘We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong dispersive waves are simultaneously generated at 2.5μm and 4.6μm. It is deciphered that the interplay between plasma currents due to Kr ionization and nonlinear effects plays a key role in DW generation. Remarkably, this kind of DW generation is corroborated by the plasma-corrected phase-matching condition.
基金Supported by the National Basic Research Programme of China under Grant No 2003CB314905, and the National Natural Science Foundation of China under Grant No 60637010.
文摘Based on the full-vector plane-wave method （FVPWM）, a hollow-core photonic crystal fibre （HC-PCF） fabricated by using the improved stack-and-draw technique is simulated. Under given propagation constants β, several effective photonie band gaps with different sizes emerge within the visible wavelength range from 575 to 720 nm. The fundamental mode and second-order mode lying in a part of PBGs are investigated. In the transmission spectrum tested, the positions of PBGs are discovered to be shifting to shorter wavelengths. The main reason is the existence of interstitial holes at nodes in the cladding region. In the later experiment, green light is observed propagating in the air-core region, and the result is more consistent with our theoretical simulation.
基金Supported by the National Natural Science Foundation of China under Grant No 60627003,and the Foundation for Creative Team in Institution of Higher Education of Guangdong Province(No 06CXTD009).
文摘For a typical photonic crystal fiber with two zero-dispersion wavelengths,we theoretically demonstrate a new way to generate supercontinuum using an input pulse of 30fs duration and lOkW peak power for providing a compact and cost effective light source to the ultra-broadband time-resolved coherent anti-Stokes Raman scattering spectroscopy.
基金Supported by the National Natural Science Foundation of China (61008036)China Postdoctoral Science Foundation(20110490779)
文摘Metal-dielectric subwavelength gratings under s-polarized and p-polarized visible radiation are studied for discovering their intriguing behaviors of spectral resonance and color property.The dependence of their resonance and color on grating parameters as well as angle of incidence and position of plane of incidence is also analyzed.For s-polarized light,the behavior of spectral resonance with single peak and higher peak efficiency is found.While transmission spectra for p-polarized light are not able to achieve a behavior like that of s-polarization,creating a perceived color is feasible.Moreover,a security grating with distinctive color shifts has been designed and its resonant properties as well as related color variation have also been provided.
基金Supported by the National Science Foundation of China under Grant Nos 60637010 and 60671036, and the National Basic Research Programme of China under Grant No 2007CB310403.
文摘We report a numerical investigation on terahertz wave propagation in plastic photonic band-gap fibres which are characterized by a 19-unit-cell air core and hexagonal Mr holes with rounded corners in cladding. Using the finite element method, the leakage loss and absorption loss are calculated and the transmission properties are analysed. The lowest loss of 0.268 dB/m is obtained. Numerical results show that the fibres could liberate the constraints of background materials beyond the transparency region in terahertz wave band, and efficiently minimize the effect of absorption by background materials, which present great advantage of plastic photonic band-gap fibres in long distance terahertz delivery.
文摘Passively Q-switched quasi-continuous-wave （QCW） diode-pumped Nd：YAG laser with Cr^4＋ ：YAG as saturable absorber is numerically investigated by solving the coupled rate equations. The threshold pump rate for passively Q-switched QCW-pumped laser is derived. The effects of the pump rate and pump-pulse duration on the laser operation characteristics are studied theoretically. The pump power range can be estimated according to the number of output pulses. The numerical simulation results are in good agreement with the experimental results.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB806002)the National High Technology Research and Development Program of China (Grant No. 2007AA03Z447)+3 种基金National Natural Science Foundation of China (Grant Nos. 60678012 and 60838004)the Foundation for Key Program of Ministry of Education, China (Grant No. 108032)FANEDD(Grant No. 2007B34)NCET (Grant No. NCET-07-0597)
文摘A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti：sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.
基金supported by the National Natural Science Foundation of China(62005193,62135008,62075158,62025504,61935015)the National Science Foundation(2114103)Guangxi Key Laboratory of Optoelectroric Information Processing(GD20202).
文摘Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics of plasmonic vortices,providing a better understanding of optical orbital angular momentums in the evanescent wave regime.However,these works only focused on the objective characterization of plasmonic vortex and have not achieved subjectively tailoring of its spatiotemporal dynamics for specific applications.Herein,it is demonstrated that the plasmonic vortices with the same topological charge can be endowed with distinct spatiotemporal dynamics by simply changing the coupler design.Based on a near-field scanning terahertz microscopy,the surface plasmon fields are directly obtained with ultrahigh spatiotemporal resolution,experimentally exhibiting the generation and evolution divergences during the whole lifetime of plasmonic vortices.The proposed strategy is straightforward and universal,which can be readily applied into visible or infrared frequencies,facilitating the development of plasmonic vortex related researches and applications.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61178028,11674243 and 11674242the National Basic Research Program of China under Grant No 2015CB755403
文摘We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrate an unambiguous interference feature in the photoelectron spectra, and the interference is unveiled to originate from the dynamic Stark effect. The interference photoelectron spectra are prompted for intense sub-femtosecond XUV laser pulses in double ionization. The stationary phase picture is corroborated qualitatively in the two-electron system. The ability of probing the dynamic Stark effect by the photoelectron spectra in a pragmatic experiment of single-photon double ionization of He may shed light on further investigation on multi-electron atoms and molecules.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11827806,11874368 and 61675213).
文摘We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.
基金Supported by the National Basic Research Programme of China under Grant No 2006CB806000, the National Natural Science Foundation of China under Grant Nos 60490280 and 60578007, NSFC-JSPS International Cooperation Programme under Grant No 60611140297, the Tianjin Natural Science Foundation under Grant No 07JCYBJC15500.
文摘We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.
文摘A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.
基金supported by the National Natural Science Foundation of China under Grant No. 60577013the New Century Support Program for Talented Young Teachers in Universities, MOE (Ministry of Education of China), China
文摘Wavelength modulation technique （WMT） and wavelength sweep technique （WST） are introduced into intra-cavity absorption gas sensors （ICAGS） for low concentration gas detection. The optimized parameters of the system maximizing the signal-to-noise ratio （SNR） are found. Calibration of acetylene concentration and gas recognition are both realized.
基金supported by the National Natural Science Foundation of China (Grant No. 10974063)the Natural Science Foundation of Hubei Province of China (Grant No. 2010CDA001)+2 种基金Ph. D. Program Foundation of the Ministry of Education of China (Grant No. 20100142110042)the Fundamental Research Funds for the Central Universities (Grant No. HUST:2010MS041)the National "973" Project (Grant No. 2007CB310403)
文摘This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the polarization of incident beam and crystal-orientation is discussed. For the experimental setup with a transceiver which transmits and detects terahertz radiation in the same crystal, we have demonstrated the optimal combination of both parameters above to optimize the working efficiency. Equations supplied in this paper are valid for zincblende crystals with arbitrary crystal- orientation and every possible polarization of an incident beam, which are of great significance for the optimization of a system.
基金Supported by the National Natural Science Foundation of China under Grant No 60671036, and the Spring Bud Project of Shandong University of Science and Technology under Grant No 2008AZZ094.
文摘A cw diode side-pumped Nd：YAO laser is frequency doubled to 532nm with an intracavity KTP crystal in a Vshaped arrangement, achieving an output power of 40 W corresponding to an optical-optical conversion efficiency of 9.7%. The instabilities and the M2-parameters of the laser are measured at different output powers after the beam is filtered.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60777036 and 60671036)the National Basic Research Program of China (Grant No. 2007CB310403)
文摘Using a double resonant KTiOPO4 （KTP） intracavity optical parametric oscillator operating at degenerated point of 2 μm, we demonstrate a unique mid-infrared source based on difference frequency generation in GaSe crystal. The output tuning range is 8.42-19.52 μm, and a peak power of 834 W for type-Ⅰ phase matching scheme and 730 W for type-Ⅱ phase matching scheme are achieved. Experimental results show that this oscillator is a good alternative to the generator of a compact and tabletop mid-infrared radiation with a widely tunable range.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10904079 and 60838001)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090031120041)the Natural Science Foundation of Tianjin (Grant No. 10JCYBJC01300)
文摘This paper numerically simulates the process of ablation of an aluminum target by an intense femtosecond laser with a fluence of 40 J/cm2 based on the two-temperature equation, and obtains the evolution of the free electron temperature and lattice temperature over a large temporal and depth range, for the first time. By investigating the temporal evolution curves of the free electron temperature and lattice temperature at three representative depths of 0, 100 nm and 500 nm, it reveals different characteristics and mechanisms of the free electron temperature evolution at different depths. The results show that, in the intense femtosecond laser ablation of aluminum, the material ablation is mainly induced by the thermal conduction of free electrons, instead of the direct absorption of the laser energy; in addition, the thermal conduction of free electrons and the coupling effect between electrons and lattice will induce the temperature of free electrons deep inside the target to experience a process from increase to decrease and finally to increase again.
