Currently,laser-induced structural modifications in optical materials have been an active field of research.In this paper,we reported structural modifications in the bulk of sapphire due to picosecond(ps)laser filamen...Currently,laser-induced structural modifications in optical materials have been an active field of research.In this paper,we reported structural modifications in the bulk of sapphire due to picosecond(ps)laser filamentation and analyzed the ionization dynamics of the filamentation.Numerical simulations uncovered that the high-intensity ps laser pulses generate plasma through multi-photon and avalanche ionizations that leads to the creation of two distinct types of structural changes in the material.The experimental bulk modifications consist of a void like structures surrounded by cracks which are followed by a submicrometer filamentary track.By increasing laser energy,the length of the damage and filamentary track appeared to increase.In addition,the transverse diameter of the damage zone increased due to the electron plasma produced by avalanche ionizations,but no increase in the filamentary zone diameter was observed with increasing laser energy.展开更多
Ultrafast laser filamentation results from the interaction of ultrafast laser with Kerr media.During filamentary propagation,the transparent medium is altered by numerous linear and nonlinear effects of ultrashort las...Ultrafast laser filamentation results from the interaction of ultrafast laser with Kerr media.During filamentary propagation,the transparent medium is altered by numerous linear and nonlinear effects of ultrashort laser pulses.Filamentation can cause material modification in solids through laser energy deposition and ionization processes,which creates a new opportunity for ultrafast laser processing of materials when combined with filamentary propagation characteristics,such as intensity champing and long propagation distance.This paper reviews the research on ultrafast laser filamentation in solids for micro-and nano-processing,including the fundamental physics,filamentation characteristics,and applications in solids for ultrafast laser filamentation-induced processing.Additionally highlighted are the difficulties and potential applications for solid-based filamentation-induced processing.展开更多
This paper reports the physical phenomenon of the temporal overlapping double femtosecond laser-induced ablation enhancement at different time delays.Detailed thermodynamic modeling demonstrates the ablation enhanceme...This paper reports the physical phenomenon of the temporal overlapping double femtosecond laser-induced ablation enhancement at different time delays.Detailed thermodynamic modeling demonstrates the ablation enhancement is highly dependent on the first pulse's laser fluence.In the case of the first pulse laser fluence being higher than material's ablation threshold,the ablation enhancement is attributed to optical absorption modification by the first pulse ablation.While the first pulse's laser fluence is lower than the material's ablation threshold,the first pulse-induced melting leads to much higher absorption of the second pulse.However,for the case of the first pulse's laser fluence even lower than melting threshold,the ablation enhancement decreases obviously with time delay.The results of the temporal overlapping double femtosecond laser ablation of poly(ε-caprolactone)are in good agreement with the theoretical predictions.展开更多
Spontaneous polarization was found in Ta_(2)O_(5)dielectric ceramics prepared by laser sintering techmique.After heat corrosion,90°and 180°domains in the ceramics was observed by field emission scanning elec...Spontaneous polarization was found in Ta_(2)O_(5)dielectric ceramics prepared by laser sintering techmique.After heat corrosion,90°and 180°domains in the ceramics was observed by field emission scanning electron micrographs.The crystal structure of the laser-si ntered ceramics at RT was determined as monocinic phase,which indicates the lattice distortion existed in the ceramics.The variation of O-Ta-O bending vibration mode was deduced from the variation of phonon mode at the low wave-mumber(57 cm^(-1)and 250cm^(-1)).The enhancement of effective electric field for tantalum atoms due to the lattice distortion was determined by calculation of charge distribution cofficients.The distortion of crystal structure due to the phase transformation from higher symmetric orthorhombic phase to lower symmetric monoclinic phase expl ained spontaneous polarization in the laser-sintered Ta_(2)O_(5)ceramics.展开更多
基金National Natural Science Foundation of China(51575013,51275011)National Key R&D Program of China(2018 YFB1107500)
文摘Currently,laser-induced structural modifications in optical materials have been an active field of research.In this paper,we reported structural modifications in the bulk of sapphire due to picosecond(ps)laser filamentation and analyzed the ionization dynamics of the filamentation.Numerical simulations uncovered that the high-intensity ps laser pulses generate plasma through multi-photon and avalanche ionizations that leads to the creation of two distinct types of structural changes in the material.The experimental bulk modifications consist of a void like structures surrounded by cracks which are followed by a submicrometer filamentary track.By increasing laser energy,the length of the damage and filamentary track appeared to increase.In addition,the transverse diameter of the damage zone increased due to the electron plasma produced by avalanche ionizations,but no increase in the filamentary zone diameter was observed with increasing laser energy.
基金supported by the National Natural Science Foundation of China (no.51975017)the National Key R&D Program of China (no.2018YFB1107500)the Scientific Research Project of Beijing Educational Committee (no.KZ202110005012)。
文摘Ultrafast laser filamentation results from the interaction of ultrafast laser with Kerr media.During filamentary propagation,the transparent medium is altered by numerous linear and nonlinear effects of ultrashort laser pulses.Filamentation can cause material modification in solids through laser energy deposition and ionization processes,which creates a new opportunity for ultrafast laser processing of materials when combined with filamentary propagation characteristics,such as intensity champing and long propagation distance.This paper reviews the research on ultrafast laser filamentation in solids for micro-and nano-processing,including the fundamental physics,filamentation characteristics,and applications in solids for ultrafast laser filamentation-induced processing.Additionally highlighted are the difficulties and potential applications for solid-based filamentation-induced processing.
基金National Research Foundation Singapore(A1883c0010)National Natural Science Foundation of China(51975017)+1 种基金China Scholarship CouncilWe wish to thank Dr. Yang Li andDr. Huagang Liu for the discussions on double-pulse laser ex periments. The support provided by China ScholarshipCouncil (CSC) during a visit of Zhenyuan Lin to theNational University of Singapore is acknowledged.
文摘This paper reports the physical phenomenon of the temporal overlapping double femtosecond laser-induced ablation enhancement at different time delays.Detailed thermodynamic modeling demonstrates the ablation enhancement is highly dependent on the first pulse's laser fluence.In the case of the first pulse laser fluence being higher than material's ablation threshold,the ablation enhancement is attributed to optical absorption modification by the first pulse ablation.While the first pulse's laser fluence is lower than the material's ablation threshold,the first pulse-induced melting leads to much higher absorption of the second pulse.However,for the case of the first pulse's laser fluence even lower than melting threshold,the ablation enhancement decreases obviously with time delay.The results of the temporal overlapping double femtosecond laser ablation of poly(ε-caprolactone)are in good agreement with the theoretical predictions.
基金National Nature Science Foundation of China(50875006)Beijing Natural Science Foundation(2082005)Scienti¯c Research Common Program of Beijing Municipal Commission of Education(KM200810005006)for their support.
文摘Spontaneous polarization was found in Ta_(2)O_(5)dielectric ceramics prepared by laser sintering techmique.After heat corrosion,90°and 180°domains in the ceramics was observed by field emission scanning electron micrographs.The crystal structure of the laser-si ntered ceramics at RT was determined as monocinic phase,which indicates the lattice distortion existed in the ceramics.The variation of O-Ta-O bending vibration mode was deduced from the variation of phonon mode at the low wave-mumber(57 cm^(-1)and 250cm^(-1)).The enhancement of effective electric field for tantalum atoms due to the lattice distortion was determined by calculation of charge distribution cofficients.The distortion of crystal structure due to the phase transformation from higher symmetric orthorhombic phase to lower symmetric monoclinic phase expl ained spontaneous polarization in the laser-sintered Ta_(2)O_(5)ceramics.
