Interference of dissociating wave packets in the I2 molecule driven by femtosecond laser pulses

The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoretically studied by using the time-dependent quantum wave packet method.Both the internuclear distanceand velocity-dependent density functions are calculated and discussed.It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses.With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs,more interference fringes can be observed,while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs,only a few interference fringes can be observed.     

Photoionization of NaK molecule with a double-well potential in femtosecond pump--probe pulse laser fields

The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump--probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6¹∑⁺ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 6¹∑⁺ state can be extracted from the photoelectron energy spectra.     

Theoretical Investigation of Femtosecond-Resolved Photoelectron Spectra of the Li2 Molecule

The time-dependent quantum wave packet method is used to investigate the dynamics for the Li2 molecule, and the time-resolved photoelectron spectra （TRPES） of the Li2 molecule are calculated. At the short delay time, the particular phenomenon of TRPES with four peaks is qualitatively interpreted in a dressed state picture by analyzing wave packet motion on light-induced potential （LIP）. The significant difference in the electronic structure of E1∑g^＋ between the inner and outer turning points has an impact on the TRPES. The control for the first excited state A1∑u^＋ of the initial wave packet is discussed.     

Study on wave packet dynamics of E~1Σ_g~+ state of Li_2 with femtosecond-resolved photoelectron spectra

Wave packet dynamics of the Li₂ molecule are investigated by using the time-dependent quantum wave packet method, and the time-resolved photoelectron spectra of the Li₂ molecule are calculated. The time-resolved wave packet theory is used to reasonably interpret the phenomena of the photoelectron spectra for different parameters. Our calculation shows that the loss of the wave packets in the shelf state area of E{ }^1\Sigma_g^ + plays a prominent role in the process of photoionization with the increase of the delay time. Moreover, the oscillation of the wave packet on the E{ }^1\Sigma_g^ + curve symbolizes a decreasing process of energy.     

Probing Wave Packet Dynamics of I2- Anions with Pump--Probe Femtosecond Spectroscopy

The wave packet dynamics of I2^- anions is studied by using the time-dependent wave packet method. Two conclusions can be drawn from the calculations. First, the period of the total photoelectron signal oscillating with the propagation of delay time is about 750fs. Second, the photoionization of I2^- anions begin at the time 600 fs, and the time needed for the population of the electronic state of I2 neutral molecule to reach the maximum becomes shorter with the increasing delay time.     

Effect of Pulse Temporal Profile on Autler-Townes Splitting in Photoelectron Spectrum

The effect of pulse temporal profiles on the Autler-Townes （AT） splitting in photoelectron spectra is theoretically studied by employing the time-dependent wave packet method for a rotational Na2 molecule. The AT splitting which results from the sufficient Rabi oscillations is affected by the pulse profile and molecular alignment. The AT splitting may be observed only by utilizing proper pulse profiles with a certain intensity.     

Theoretical Investigation of Femtosecond-Resolved Photoelectron Spectrum of NaI Molecules

The time-resolved photoelectron spectra （TRPES） of NaI molecules are calculated by using the time-dependent wave packet method. Two different potential energy curves （adiabatic and diabatic） are adopted in the simulation. The third peak of the photoelectron spectra presented in the adiabatic calculation is induced by the reflection of the wave packet. The oscillating of the wave packet onto the diabatic energy curve is a decreasing process. The comparison of the photoelectron spectra between the two different calculations （adiabatic and diabatic） is presented.     

Autler-Townes splitting in photoelectron spectra of K2 molecule

We investigate Autler-Townes splitting in the photoelectron spectra of K₂ molecule driven by pump-probe pulses via employing the time-dependent wave packet approach.It is found that the magnitude of Aulter-Townes splitting varies with the wavelength of the intense laser pulse.In particular,the phenomenon of Aulter-Townes splitting vanishes for the far-off resonance of the pump pulse.Also,the split peaks of Autler-Townes in the case of resonant pump pulse give us an approach to directly obtaining the transition dipole moment of a molecule.     

Effect of pump-1 laser on Autler Townes splitting in photoelectron spectrum of K2 molecule

We theoretically investigate the Autler–Townes(AT)splitting in the photoelectron spectrum of four-level ladder K2molecule driven by a pump 1-pump 2-probe pulse via employing the time-dependent wave packet approach.The effects of the pump-1 laser intensity and wavelength on AT splitting are studied for the first time.The magnitude of AT splitting increases with increasing the pump-1 laser intensity.The triple splitting with asymmetric profile occurs due to the nonresonant excitation.The triple structure is transformed into a double structure(near-resonant region),and then becomes a peak(far-off resonant region)progressively as the pump-1 laser is detuned from the resonance wavelength,which can be explained in terms of the asymmetric excitation/population of dressed states.The splitting between adjacent peaks and the splitting between the two sideband peaks in the triplet do not change with the pump-1 pulse wavelength.The three peaks shift toward lower energy with the same shift 1/4*△1 as the pump-1 wavelength changes in near-resonant region.The asymptotic behaviors of AT splitting with the pump-1 laser intensity are interesting in the threshold points of the near-resonant region and the far-off resonant region.     

Theoretical analysis of the electromagnetic field inside an anomalous-dispersion microresonator under synthetical pump

We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato–Lefever equation. Unlike the traditional single continuous wave(CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted.The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field.     

Autler-Townes Splitting in Photoelectron Spectrum of Three-Level Li2 Molecule in Ultrashort Pulse Laser Fields

The Autler-Townes （AT） splitting in femtosecond photoelectron spectrum of three-level Li2 molecules is theoretically investigated using time-dependent quantum wave packet method. With proper femtosecond laser pulses, three peaks of the AT splitting can be observed in the photoelectron spectrum. The AT splitting stems from rapid Rabi oscillation caused by intense ultrashort laser pluses. The effects of laser parameters on the molecular ionization dynamics are also discussed.     

Optical Transient Relaxation of an Ag—BaO Composite Thin Film with a Supercontinuum Probe

The optical transient absorption spectra of an Ag-BaO thin film have been detected at a wavelength ranging from 400nm to 1000nm using the pump supercontinuum probe technique with a resolution of 130fs.We have observed the optical ultrafast relaxation,in which the electrons near the Fermi level of Ag nanoparticles were excited to a non-equilibrium state and then returned to an equilibrium state.The decay time was exponentially fitted and varied from 0.67ps to 4ps for different components of the supercontinuum probe.The peak of an unoccupied state for silver at level X‘4 was estimated to be 1.47eV above the Fermi level.     

High-Fidelity Manipulation of the Quantized Motion of a Single Atom via Stern–Gerlach Splitting

We demonstrate high-fidelity manipulation of the quantized motion of a single~(87)Rb atom in an optical tweezer via microwave couplings induced by Stern–Gerlach splitting. The Stern–Gerlach splitting is mediated by polarization gradient of a strongly focused tweezer beam that functions as fictitious magnetic field gradient. The spatial splitting removes the orthogonality of the atomic spatial wavefunctions, thus enables the microwave couplings between the motional states. We obtain coherent Rabi oscillations for up to third-order sideband transitions, in which a high fidelity of larger than 0.99 is obtained for the spin-flip transition on the first order sideband after subtraction of the state preparation and detection error. The Stern–Gerlach splitting is measured at a precision of better than 0.05 nm. This work paves the way for quantum engineering of motional states of single atoms, and may have wide applications in few body physics and ultracold chemistry.     

Field-free molecular orientation induced by combined femtosecond single- and dual-color laser pulses：The role of delay time and quantum interference

The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6.     

Interference effect of photoionization of hydrogen atoms by ultra-short and ultra-fast high-frequency chirped pulses

The photoionization of a hydrogen atom from its ground state with ultra-fast chirped pulses is investigated by numerically solving the time-dependent Schr¨odinger equation within length, velocity, and Kramers–Henneberger gauges.Converged results for all gauges for chirp-free pulses agree with the prediction of dynamic interference for ground state hydrogen atoms predicted recently by Jiang and Burgd¨orfer [Opt. Express 26, 19921(2018)]. In addition, we investigated photoelectron spectra of hydrogen atoms by chirped laser pulses, and showed that dynamic interference effect will be weaken for pulses with increasing linear chirp. Our numerical results can be understood and discussed in terms of an interplay of photoelectron wavepackets from first and second halves of laser enevelop, including the ac Stark energy level shift of the photoelectron final state and atomic stabilization effect at ultra-high intensities.     

Quantum interference in laser-assisted photo-ionization excited by a femtosecond x-ray pulse

The photoelectron energy spectra （PESs） excited by monochromatic femtosecond x-ray pulses in the presence of a femtosecond laser are investigated. APES is composed of a set of separate peaks, showing interesting comb-like structures. These structures result from the quantum interferences between photoelectron wave packets generated at different times. The width and the localization of each peak as well as the number of peaks are determined by all the laser and x-ray parameters. Most of peak heights of the PES are higher than the classical predictions.     

Active manipulation of the selective alignment by two laser pulses

This paper solves numerically the full time-dependent Schrdinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant.     

Influence of laser fields on the vibrational population of molecules and its wave-packet dynamical investigation

The time-dependent wave packet method is used to investigate the influence of laser-fields on the vibrational population of molecules.For a two-state system in laser fields,the populations on different vibrational levels of the upper and lower electronic states are given by wavefunctions obtained by solving the Schro¨dinger equation with the splitoperator method.The calculation shows that the field parameters,such as intensity,wavelength,duration,and delay time etc.can have different influences on the vibrational population.By varying the laser parameters appropriately one can control the evolution of wave packet and so the vibrational population in each state,which will benefit the light manipulation of atomic and molecular processes.     

Laser-Induced Continuum Structure of NO Molecules in Two-Colour Femtosecond Pulsed Laser Fields

The method of quantum wave packet dynamics is used to study the multiphoton ionization of NO molecules via a two-photon Raman coupling and a laser-induced continuum structure （LICS） state in two-colour strong femtosecond pulsed laser fields. Time-and energy-resolved photoelectron energy spectra are calculated for describing three photoionization channels. The population transfers through the LICS and the Raman coupling passages are discussed.     

Separation and insertion of optical bit-serial label in optical packet switching

The bipolar phase-shift-keying (BPSK) optical orthogonal codes (OOCs) are inserted into the optical packet format of bit-serial label. The ultra-fast separation of the label and payload is performed through the auto-correlation pulses indicating the time position at which the optical switch changes the state. The insertion of the new label can also be realized by detecting the auto-correlation pulse at the line rate. Especially, the scheme can be adapted to the asynchronous separation and insertion and realize the variable-length packet switching. The results of simulation verify the feasibility of the scheme.