Vortex beams with fractional topological charge(FTC) have many special characteristics and novel applications.However, one of the obstacles for their application is the difficulty of precisely determining the FTC of f...Vortex beams with fractional topological charge(FTC) have many special characteristics and novel applications.However, one of the obstacles for their application is the difficulty of precisely determining the FTC of fractional vortex beams. We find that when a vortex beam with an FTC illuminates a dynamic angular double slit(ADS), the far-field interference patterns that include the information of the FTC of the beam at the angular bisector direction of the ADS vary periodically. Based on this property, a simple dynamic ADS device and data fitting method can be used to precisely measure the FTC of a vortex light beam with an error of less than 5%.展开更多
The method of nonlinear parabolized stability equations（PSE） is applied in the simulation of vortex structures in compressible mixing layer.The spatially-evolving unstable waves,which dominate the vortex structure,a...The method of nonlinear parabolized stability equations（PSE） is applied in the simulation of vortex structures in compressible mixing layer.The spatially-evolving unstable waves,which dominate the vortex structure,are investigated through spatial marching method.The instantaneous flow field is obtained by adding the harmonic waves to basic flow.The results show that T-S waves do not keep growing exponentially as the linear evolution,the energy transfer to high order harmonic modes,and that finally all harmonic modes get saturated due to nonlinear interaction.The mean flow distortion induced by the nonlinear interaction between the harmonic modes and their conjugate harmonic ones,makes great change of the average flow and increases the thickness of mixing layer. PSE methods can well capture the two- and three-dimensional large scale nonlinear vortex structures in mixing layers such as vortex roll-up,vortex pairing,and A vortex.展开更多
基金Fundamental Research Funds for the Central UniversitiesNational Natural Science Foundation of China(NSFC)(11374008,11374238,11374239,11534008)
文摘Vortex beams with fractional topological charge(FTC) have many special characteristics and novel applications.However, one of the obstacles for their application is the difficulty of precisely determining the FTC of fractional vortex beams. We find that when a vortex beam with an FTC illuminates a dynamic angular double slit(ADS), the far-field interference patterns that include the information of the FTC of the beam at the angular bisector direction of the ADS vary periodically. Based on this property, a simple dynamic ADS device and data fitting method can be used to precisely measure the FTC of a vortex light beam with an error of less than 5%.
基金supported by the National Natural Sci- ence Foundation of China(11102198)
文摘The method of nonlinear parabolized stability equations（PSE） is applied in the simulation of vortex structures in compressible mixing layer.The spatially-evolving unstable waves,which dominate the vortex structure,are investigated through spatial marching method.The instantaneous flow field is obtained by adding the harmonic waves to basic flow.The results show that T-S waves do not keep growing exponentially as the linear evolution,the energy transfer to high order harmonic modes,and that finally all harmonic modes get saturated due to nonlinear interaction.The mean flow distortion induced by the nonlinear interaction between the harmonic modes and their conjugate harmonic ones,makes great change of the average flow and increases the thickness of mixing layer. PSE methods can well capture the two- and three-dimensional large scale nonlinear vortex structures in mixing layers such as vortex roll-up,vortex pairing,and A vortex.
