The Study On Generation And Measurement Of The Novel Structured Light

Structured light field,that is,the light field after phase,amplitude or polarization is modulated specially.Vortex beam is one of the most novel and potential light fields in the new structured light field.Because of its special spiral phase structure and the characteristics of carrying orbital angular momentum(OAM),vortex light has broad application prospects in many fields such as optical drive micromechanics,quantum information and optical micromanipulation.The study of vortex light has become an important further line in modern optics and physics,and the generation and detection methods of vortex beams are the basis and means for studying the transmission characteristics of such beams and carrying out related application research.The main characteristics of vortex beams are concentrated in orbital angular momentum,so how to generate and detect vortex beams with specific orbital angular momentum spectrum is very critical.In this context,this dissertation firstly proposes the concepts of two new structured light fields,namely open vortex beam and new non-diffraction vortex beam.Through studying their transmission characteristics by functional equation and light diffraction theory,the basic characteristics of vortex beam verified by experimental methods are also elaborated.Then,an improved mulitipoint interferometry method is proposed to detect the topological charge of vortex light,which resolves the problem that the traditional mulitipoint interferometry method cannot detect the high-order topological charge vortex beam,and greatly improves the detection range of this method.Finally,based on mulitipoint interferometry and scalar diffraction method,a new scheme that can generate and detect vortex beams carrying specific orbital angular momentum spectrum is proposed,and theoretical and experimental studies are both carried out in depth on the petal-shaped vortex beam and orbital angular momentum comb.The main innovations are as follows:1.The main innovation points are: two new structured light fields are innovatively proposed and analyzed,namely the open vortex beam with open-loop structure and the new non-diffraction vortex beam with non-diffraction characteristics.The equation formula of the open vortex beam was innovatively established,and the transmission characteristics of the open vortex beam are analyzed by using the resulted equation formula.A new type of partial fork grating is creatively proposed for generating open vortex beams.For the first time,the generation and transmission characteristics of open vortex beams and new non-diffraction beams were tested in the laboratory.2.The main innovation points are: an improved mulitipoint interferometry method is innovatively proposed for detecting orbital angular momentum.From the perspective of physical analysis,the influence of diffraction aperture on the periodic repetition of interference images is explained.For the first time,vortex beams with high topological charge were accurately measured using mulitipoint interferometry in the laboratory.3.The main innovation points are: a mulitipoint interferometry with spiral structure innovatively proposed to generate and manipulate the orbital angular momentum spectrum.The concept of orbital angular momentum comb is pioneered in this dissertation.For the first time,a specific orbital angular momentum spectrum was generated manipulatively by mulitipoint interferometry in the laboratory.The major research contents are specifically as follows:1.The far-field characteristics and the light intensity distribution along the transmission process of the open vortex beam generated by the fork grating with different parameters are calculated by simulation method.A new type of non-diffraction vortex beam was generated by mulitipoint interferometry,and the transmission characteristics of such beam are studied by simulation calculation based on diffraction theory.By comparing with the vortex beam generated by the spiral holographic method,its transmission characteristics of non-diffraction are further elaborated.By using experimental research methods,it is proved that the far-field light intensity,phase distribution,and the beam characteristics during the transmission of open vortex beam and new non-diffraction beam are in good agreements with the theoretical results.In addition,the topological charge and ancient phase shift characteristics of the open vortex beam have also been verified.The results show that the open vortex beam and the new non-diffraction vortex beam,though as new structured light fields with obvious unique characteristics,still have the basic characteristics of traditional vortex beams,such as stable transmission characteristics and conservation of orbital angular momentum.Such new vortex beams have a great potential in the fields of micro-nano particle manipulation,optical detection and laser processing.2.The far-field expression of vortex beam passing through the mulitipoint mask was obtained by the Fraunhofer diffraction theory.The influence of the aperture of the small hole on the interference pattern was analyzed theoretically,and the physical mechanism of periodic repetition of the interference image of the traditional mulitipoint interferometry method appering with the increase of the topological charge was explained.Through theoretical analysis and numerical simulation,it is proved that the improved mulitipoint interferometry method can detect vortex beams with high topological charge,and have no problem of periodic duplication of interference images.This new method adopts a larger aperture diffraction hole,which can obtain more incident light phase information,so it can detect vortex light with a larger topological charge.In addition,it is proved that this method can be widely used to measure the topological charges of vortex beams such as Bessel-Gauss beam and Laguerre-Gauss beam,and has good robustness to be used in other scalar vortex fields,such as electron vortex beams,neutron vortex beams and X-ray vortex beams.Finally,an experimental device with improved mulitipoint interferometry was built to detect far-field interference images of vortex beam with distinct orbital angular momentum,and the experimental results were highly consistent with the theoretical simulation results.The study shows that this method has highly application value in detecting the orbital angular momentum of large-size and lowpower beams.3.Through the calculation based on Huygens-Fresnel diffraction integral formula,it is proved that the plane beam can be converted into a vortex beam with specific orbital angular momentum spectrum by the method of mulitipoint mask with helical structure.And such method shown by studying the generated petal-shaped vortex beam(photon gear)and orbital angular momentum comb has been proved to generate a variety of specially structured beam fields.This method has also been proved experimentally to generate vortex beams with specific orbital angular momentum spectrum easily.By the experimental study of mode decomposition method,it is proved that the OAM spectrum that generate vortex beams are highly consistent with the design values,and the concise experimental device demonstrates that this method is suitable for optical communication and quantum information and other related applications.The results show that although the experimental verification of mulitipoint interferometry used the case of optical vortex,it is not limited to the optical field,but also can be widely used in other complex scalar vortex fields,such as electron,neutron,acoustic and radio vortex.