Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to comp...Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.展开更多
We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting...We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.展开更多
Random lasing was experimentally investigated in pyrromethene 597-doped strongly disordered chiral liquid crystals (CLCs) composed of the nematic liquid crystal SLC1717 and the chiral agent CB15. The concentration of ...Random lasing was experimentally investigated in pyrromethene 597-doped strongly disordered chiral liquid crystals (CLCs) composed of the nematic liquid crystal SLC1717 and the chiral agent CB15. The concentration of the chiral agent tuned the bandgap, and disordered CLC microdomains were achieved by fast quenching of the mixture from the isotropic to the cholesteric phase. Random lasing and band edge lasing were observed synchronously, and their behavior changed with the spectral location of the bandgap. The emission band for band edge lasing shifted with the change of the bandgap, while the emission band for random lasing remained practically constant. The results show that the threshold for random lasing sharply decreases if the CLC selective reflection band overlaps with the fluorescence peak of the dye molecules and if the band edge coincides at the same time with the excitation wavelength.展开更多
基金National Key Research and Development Program of China(no.2021YFA1400200)National Natural Science Foundation of China(nos.12025407,11934003,and 12204513)“Strategic Priority Research Program(B)”of Chinese Academy of Sciences(grant nos.XDB330301 and YSBR047).
文摘Laser-induced melting plays a crucial role in advanced manufacturing technology and ultrafast science;however,its atomic processes and microscopic mechanisms,especially in a wide-gap ceramic,remain elusive due to complex interplays between many degrees of freedom within a timescale of~100 fs.We report here that laser melting is greatly accelerated by intense laser-induced tunnel ionization,instead of a priori multiphoton absorption,in the archetypal ceramic magnesium oxide(MgO).The tunneling processes generate a large number of photocarriers and results in intense energy absorption,instantaneously altering the potential energy surface of lattice configuration.The strong electron–phonon couplings and fast carrier relaxation enable efficient energy transfer between electrons and the lattice.These results account well for the latest ultrafast melting experiments and provide atomistic details and nonequilibrium mechanism of photoinduced ultrafast phase transitions in wide-gap materials.The laser modulation of melting thresholds and phase boundary demonstrate the possibility of manipulating phase transition on demand.A shock wave curve is also obtained at moderate conditions(P=2 GPa),extending Hugoniot curve to new regimes.
基金supported by the National Natural Science Foundation of China(No.11674182)the National Basic Research Program of China(No.2013CB328702)+5 种基金the Tianjin Natural Science Foundation(No.17JCYBJC16700)the 111 Project(No.B07013)the PCSIRT(No.IRT_13R29)the National Research Program of Slovenia(No.P1-0192)the Hundred Young Academic Leaders Program of Nankai Universitythe Collaborative Innovation Center of Extreme Optics,Shanxi University
文摘We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.
基金National Key Research and Development Program of China(2017YFA0303800)National Natural Science Foundation of China(91750204,11674182)+4 种基金111Project(B07013)Natural Science Foundation of Tianjin City(17JCYBJC16700)Slovenian Research Agency(ARRS,Research Program P1-0192)Project of National Academy of Sciences of Ukraine(0117U002612)Projects of National Academy of Sciences of Ukraine(V-197,VC-202)。
文摘Random lasing was experimentally investigated in pyrromethene 597-doped strongly disordered chiral liquid crystals (CLCs) composed of the nematic liquid crystal SLC1717 and the chiral agent CB15. The concentration of the chiral agent tuned the bandgap, and disordered CLC microdomains were achieved by fast quenching of the mixture from the isotropic to the cholesteric phase. Random lasing and band edge lasing were observed synchronously, and their behavior changed with the spectral location of the bandgap. The emission band for band edge lasing shifted with the change of the bandgap, while the emission band for random lasing remained practically constant. The results show that the threshold for random lasing sharply decreases if the CLC selective reflection band overlaps with the fluorescence peak of the dye molecules and if the band edge coincides at the same time with the excitation wavelength.
