A new approach is presented to reveal the temporal structure of femtosecond laser pulses by recording the correspond- ing time-resolved shadowgraphs of the laser-induced air plasma. It is shown that the temporal struc...A new approach is presented to reveal the temporal structure of femtosecond laser pulses by recording the correspond- ing time-resolved shadowgraphs of the laser-induced air plasma. It is shown that the temporal structures of femtosecond laser pulses, normally not observable by the ordinary intensity autocorrelator, can be detected through intuitively analyz- ing the ultrafast evolution process of the air plasma induced by the femtosecond laser pulses under examination. With this method, existence of pre- and post-pulses has been clearly unveiled within the time window of 4-150 fs in reference with the main 50-fs laser pulses output from a commercial 1-kHz femtosecond laser amplifier. The unique advantage of the proposed method is that it can directly provide valuable information about the pulse temporal structures＇ effect on the laser-induced ionization or material ablation.展开更多
At present,spark plugs are used to trigger discharge in pulsed plasma thrusters（PPT）,which are known to be life-limiting components due to plasma corrosion and carbon deposition.A strong electric field could be form...At present,spark plugs are used to trigger discharge in pulsed plasma thrusters（PPT）,which are known to be life-limiting components due to plasma corrosion and carbon deposition.A strong electric field could be formed in a cathode triple junction（CTJ） to achieve a trigger function under vacuum conditions.We propose an induction-triggered electrode structure on the basis of the CTJ trigger principle.The induction-triggered electrode structure could increase the electric field strength of the CTJ without changing the voltage between electrodes,contributing to a reduction in the electrode breakdown voltage.Additionally,it can maintain the plasma generation effect when the breakdown voltage is reduced in the discharge experiments.The induction-triggered electrode structure could ensure an effective trigger when the ablation distance of Teflon increases,and the magnetic field produced by the discharge current could further improve the plasma density and propagation velocity.The induction-triggered coaxial PPT we propose has a simplified trigger structure,and it is an effective attempt to optimize the micro-satellite thruster.展开更多
By simultaneously employing both an electro-optic modulator and carbon nanotube saturable absorber(CNT-SA)in a dual-loss modulator, a subnanosecond single mode-locking pulse underneath a Q-switched envelope with high ...By simultaneously employing both an electro-optic modulator and carbon nanotube saturable absorber(CNT-SA)in a dual-loss modulator, a subnanosecond single mode-locking pulse underneath a Q-switched envelope with high peak power was generated from a doubly Q-switched and mode-locked(QML) Nd:Lu_(0.15)Y_(0.85)VO_4 laser at1.06 μm for the first time, to our knowledge. CNTs with different wall structures—single-walled CNTs(SWCNTs),double-walled CNTs(DWCNTs), and multi-walled CNTs(MWCNTs)—were used as SAs in the experiment to investigate the single mode-locking pulse characteristics. At pump power of 10.72 W, the maximum peak power of1.312 MW was obtained with the DWCNT.展开更多
Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabil...Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabilities.However,achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions,given their polychromatic bandwidth.This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior.We developed a comprehensive approach to directly design and govern these laser pulses.This method elucidates the role jointly played by the pulse's spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics.It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses.By tailoring the prescribed phase gradient,we demonstrate the creation of,to our knowledge,novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries.The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail.For instance,the intensity peak can be configured as a THz rotating light spot or shaped as a curve,enabling simultaneous substrate illumination at rates of tens of THz,far exceeding the MHz rates typically used in laser material processing.Additionally,the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam.Together,these advancements unveil advantageous capabilities that have been sought after for many years,especially in ultrafast optics and light-matter interaction research.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11004111 and 61137001)the Natural Science Foundation of Tianjin City,China (Grant No. 10JCZDGX35100)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20100031120034)the Fundamental Research Funds for the Central Universities of China
文摘A new approach is presented to reveal the temporal structure of femtosecond laser pulses by recording the correspond- ing time-resolved shadowgraphs of the laser-induced air plasma. It is shown that the temporal structures of femtosecond laser pulses, normally not observable by the ordinary intensity autocorrelator, can be detected through intuitively analyz- ing the ultrafast evolution process of the air plasma induced by the femtosecond laser pulses under examination. With this method, existence of pre- and post-pulses has been clearly unveiled within the time window of 4-150 fs in reference with the main 50-fs laser pulses output from a commercial 1-kHz femtosecond laser amplifier. The unique advantage of the proposed method is that it can directly provide valuable information about the pulse temporal structures＇ effect on the laser-induced ionization or material ablation.
基金National Natural Science Foundation of China(No.51577011)the Graduate Innovation Project of Beijing Jiaotong University(No.2016YJS147) for the financial support of this work
文摘At present,spark plugs are used to trigger discharge in pulsed plasma thrusters（PPT）,which are known to be life-limiting components due to plasma corrosion and carbon deposition.A strong electric field could be formed in a cathode triple junction（CTJ） to achieve a trigger function under vacuum conditions.We propose an induction-triggered electrode structure on the basis of the CTJ trigger principle.The induction-triggered electrode structure could increase the electric field strength of the CTJ without changing the voltage between electrodes,contributing to a reduction in the electrode breakdown voltage.Additionally,it can maintain the plasma generation effect when the breakdown voltage is reduced in the discharge experiments.The induction-triggered electrode structure could ensure an effective trigger when the ablation distance of Teflon increases,and the magnetic field produced by the discharge current could further improve the plasma density and propagation velocity.The induction-triggered coaxial PPT we propose has a simplified trigger structure,and it is an effective attempt to optimize the micro-satellite thruster.
基金National Natural Science Foundation of China(NSFC)(61378022)Fundamental Research Funds of Shandong University(2014JC032)
文摘By simultaneously employing both an electro-optic modulator and carbon nanotube saturable absorber(CNT-SA)in a dual-loss modulator, a subnanosecond single mode-locking pulse underneath a Q-switched envelope with high peak power was generated from a doubly Q-switched and mode-locked(QML) Nd:Lu_(0.15)Y_(0.85)VO_4 laser at1.06 μm for the first time, to our knowledge. CNTs with different wall structures—single-walled CNTs(SWCNTs),double-walled CNTs(DWCNTs), and multi-walled CNTs(MWCNTs)—were used as SAs in the experiment to investigate the single mode-locking pulse characteristics. At pump power of 10.72 W, the maximum peak power of1.312 MW was obtained with the DWCNT.
基金Ministerio de Ciencia,Innovación y Universidades(PID2021-125483NB-I00,PGC2018-095595-B-I00)。
文摘Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabilities.However,achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions,given their polychromatic bandwidth.This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior.We developed a comprehensive approach to directly design and govern these laser pulses.This method elucidates the role jointly played by the pulse's spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics.It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses.By tailoring the prescribed phase gradient,we demonstrate the creation of,to our knowledge,novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries.The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail.For instance,the intensity peak can be configured as a THz rotating light spot or shaped as a curve,enabling simultaneous substrate illumination at rates of tens of THz,far exceeding the MHz rates typically used in laser material processing.Additionally,the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam.Together,these advancements unveil advantageous capabilities that have been sought after for many years,especially in ultrafast optics and light-matter interaction research.
