The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfe...The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.展开更多
Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 1...Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd：YAG and Nd：GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors （SESAMs） was relevant to the upper-state lifetime and the emission cross-section of the gain medium.展开更多
An asynchronous optical sampling scheme based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF） is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is su...An asynchronous optical sampling scheme based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF） is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source （SPS）. 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented.展开更多
Using molecular dynamics (MD) methods combining with two-step radiation heating model, the mechanisms of ablation and the thermodynamic states at Ni surface under femtosecond laser irradiation are investigated. Simula...Using molecular dynamics (MD) methods combining with two-step radiation heating model, the mechanisms of ablation and the thermodynamic states at Ni surface under femtosecond laser irradiation are investigated. Simulation results show that the main mechanisms of ablation are evaporation and tensile stresses generated inside the target. The velocity of stress wave is predicted to be nearly equal to sound velocity. The rates of ablation at different fluences obtained from simulations are in good agreement with experimental data. Superheating phen omenon is also discovered.展开更多
基金The work was supported by the National Natural Sci-ence Foundation of China (No. 10234030 and 60478002)and the Natural Science Foundation of Shanghai (No.04JC14036 and 03ZR14102)
文摘The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.
基金This work was supported by the National Nature Science Foundation of Beijing under Grant No. 3021001 and the foundation of Liaocheng University.
文摘Ultrashort pulses were generated in passively mode-locked Nd：YAC and Nd：CdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd：YAG and Nd：GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors （SESAMs） was relevant to the upper-state lifetime and the emission cross-section of the gain medium.
基金supported by the project of the Vital Instrument Research of CAS (No. YZ200759)and the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘An asynchronous optical sampling scheme based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF） is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source （SPS）. 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented.
文摘Using molecular dynamics (MD) methods combining with two-step radiation heating model, the mechanisms of ablation and the thermodynamic states at Ni surface under femtosecond laser irradiation are investigated. Simulation results show that the main mechanisms of ablation are evaporation and tensile stresses generated inside the target. The velocity of stress wave is predicted to be nearly equal to sound velocity. The rates of ablation at different fluences obtained from simulations are in good agreement with experimental data. Superheating phen omenon is also discovered.
