The Measurement Method Of Coherence Vortices In Partially Coherent Beams Based On Correlation Imaging

As an important branch of modern singularity optics,optical vortices have broad application prospects and development prospects in many fields,such as space optical communication,optical micro-operation,laser optics,optical superresolution and nonlinear optics.Vortex beams ha ve we ll-defined orbita l angular mo ment um because of its specia l he lical wa ve fronts,whic h makes them have infinite potentia l.In recent years,the measure me nt of optica l vort ices has expanded from coherent case to partially coherent case.In this thes is,the measure me nt met hod of coherent vortices in partially coherent beams is studied theoretically.The main contents are as follows:1?The genera l s it uat ion o f optica l vort ices,the theoret ical mode l describ ing partia lly coherent beams and the propagation theory of partia lly coherent beams are introduced.2?The principle of correlation imaging is introduced.The analytical expressions o f incoherent Laguerre-Gauss(LG_0m)beams with radial index of 0 and angular index of m propagating in correlation imaging devices are derived.The incoherent vortices in beams are measured by designing special object transmission functions.The results show that the cross spectral density?CSD?of the detectors can be obtained by scanning the parameters s of the object's transmission function when the condition of s=m is satisfied.3?The concept of multiplexing coherent vortices used in optical communication systems is introduced.A device for generating two-mode coherent vortices beam is proposed.A theoretical study of the method for measuring coherent vortices is carried out.On this basis,whether the method can discriminate the topological charge in coherent vortices multiplexing is verified.A method for discriminating the topological charge in multiplexed incoherent Laguerre-Gauss(LG_0m)beams based on correlation imaging is proposed.The analysis shows that when the parameter s in the transmission function of the scanned object is equal to the topological charge m of the mode in the multiplexed optical field,we can get the corresponding information in the signal intensity of the cross spectral density?CSD?in the detector and further infer the weight of each mode.The signal intensity of CSD increases rapidly with the increase of the topological load,which is beneficial to the measurement of higher order modes.