Measuring The Cross-spectral Density Of A Partially Coherent Vector Beam

Since the invention of the laser in the 1960s,research on laser characteristics and applications has developed rapidly.A variety of new light fields with special spatial distribution such as amplitude,phase,polarization,and coherent structure are proposed and realized.The unique properties and applications of new light fields have attracted great attention from researchers.In the past,the laser research tended to focus on the full coherence beam.But in recent years,research has shown that reducing the coherence of beams can also have a positive effect.For example,it has more uniform intensity distribution,weakened speckle effect,stronger anti-turbulence,better diffraction imaging,and so on.At the same time,vector beam is widely studied in information storage,material processing,and polarization imaging due to its rich polarization characteristics.Therefore,partially coherent vector beams,which are controlled by coherence and polarization,have been proposed and presented rich new physical effects and application prospects.However,how to measure the partially coherent vector beam,especially the imaginary part and cross term of the cross spectral density,has not been solved,which limits its application to a certain extent.This thesis introduces the polarization and coherent theory of the light with partially coherent beam,measuring the cross-spectral density of a partially coherent vector beam via self-referencing holography is proposed.The specially correlation radially polarized beams and the off-axis specially correlation radially polarized beams are constructed.The partially coherent vector beams are measured experimentally.Young’s double slit experiment for partially coherent vortex beams is studied,and the phase of the cross-spectral density of the focal field after partially coherent vortex beams pass through the double-slit is measured by self-reference holography.Topological charges of partially coherent vortex beams can be determined from the phase distribution of cross-spectral density.We also used this method to solve the problem of microphase imaging under partially coherent illumination,and the morphology of cervical exfoliated cells was measured by self-reference holography.We can distinguish the normal and shrinking lesion cervical exfoliated cells by their amplitude and phase.Finally,our summary and prospects of partially coherent beam in coherent diffraction imaging are presented.