The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer st...The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.展开更多
Attosecondattosecond science;extreme ultraviolet;high-order harmonic generation;Ramsey-type spectroscopy Optical and Ramsey-Type Interferometry by Postgeneration Splitting of Harmonic PulseTime domain Ramsey-type inte...Attosecondattosecond science;extreme ultraviolet;high-order harmonic generation;Ramsey-type spectroscopy Optical and Ramsey-Type Interferometry by Postgeneration Splitting of Harmonic PulseTime domain Ramsey-type interferometry is useful for investigating spectroscopic information of quantum states in atoms and molecules.The energy range of the quantum states to be observed with this scheme has now reached more than 20 eV by resolving the interference fringes with a period of a few hundred attoseconds.This attosecond Ramsey-type interferometry requires the irradiation of a coherent pair of extreme ultraviolet(XUV)light pulses,while all the methods used to deliver the coherent XUV pulse pair until now have relied on the division of the source of an XUV pulse in two before the generation.In this paper,we report on a novel technique to perform attosecond Ramsey-type interferometry by splitting an XUV high-order harmonic(HH)pulse of a sub-20 fs laser pulse after its generation.By virtue of the postgeneration splitting of the HH pulse,we demonstrated that the optical interference emerging at the complete temporal overlap of the HH pulse pair seamlessly continued to the Ramsey-type electronic interference in a helium atom.This technique is applicable for studying the femtosecond dephasing dynamics of electronic wavepackets and exploring the ultrafast evolution of a cationic system entangled with an ionized electron with sub-20 fs resolution.展开更多
This work is concerned with the numerical simulations on the Gierer-Meinhardt activator-inhibitor models. We consider the case when the inhibitor timeconstant τ is non-zero. In this case, oscillations and pulse split...This work is concerned with the numerical simulations on the Gierer-Meinhardt activator-inhibitor models. We consider the case when the inhibitor timeconstant τ is non-zero. In this case, oscillations and pulse splitting are observed numerically.Numerical experiments are carried out to investigate the dynamical behaviorsand instabilities of the spike patterns. The numerical schemes used are based upon anefficient moving mesh finite element method which distributes more grid points nearthe localized spike regions.展开更多
基金supported by National Basic Research Program of China under Grant No.2014CB339802,No.2011CB808100National Natural Science Foundation of China under Grant No.11174156
文摘The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.
基金supported by the Core Research for Evolutional Science and Technology(JPMJCR15N1)of JSTthe Center of Innovation Program(JPMJCE1313)of JST+2 种基金a Grant-in-Aid for Specially Promoted Research(JP15H05696)from MEXTGrants-in-Aid for Scientific Research(19H00869,19H05628,20H00371,26247068,20H05670)from MEXTthe Quantum Leap Flagship Program(JPMXS0118068681,JPMXS0118067246)of MEXT,Japan.
文摘Attosecondattosecond science;extreme ultraviolet;high-order harmonic generation;Ramsey-type spectroscopy Optical and Ramsey-Type Interferometry by Postgeneration Splitting of Harmonic PulseTime domain Ramsey-type interferometry is useful for investigating spectroscopic information of quantum states in atoms and molecules.The energy range of the quantum states to be observed with this scheme has now reached more than 20 eV by resolving the interference fringes with a period of a few hundred attoseconds.This attosecond Ramsey-type interferometry requires the irradiation of a coherent pair of extreme ultraviolet(XUV)light pulses,while all the methods used to deliver the coherent XUV pulse pair until now have relied on the division of the source of an XUV pulse in two before the generation.In this paper,we report on a novel technique to perform attosecond Ramsey-type interferometry by splitting an XUV high-order harmonic(HH)pulse of a sub-20 fs laser pulse after its generation.By virtue of the postgeneration splitting of the HH pulse,we demonstrated that the optical interference emerging at the complete temporal overlap of the HH pulse pair seamlessly continued to the Ramsey-type electronic interference in a helium atom.This technique is applicable for studying the femtosecond dephasing dynamics of electronic wavepackets and exploring the ultrafast evolution of a cationic system entangled with an ionized electron with sub-20 fs resolution.
文摘This work is concerned with the numerical simulations on the Gierer-Meinhardt activator-inhibitor models. We consider the case when the inhibitor timeconstant τ is non-zero. In this case, oscillations and pulse splitting are observed numerically.Numerical experiments are carried out to investigate the dynamical behaviorsand instabilities of the spike patterns. The numerical schemes used are based upon anefficient moving mesh finite element method which distributes more grid points nearthe localized spike regions.
