Coherence Structure Measurement And Tightly Focused Characteristics Of Vector Partially Coherent Light Field

The National Fourteenth Five-Year Plan clearly states that the development of major innovation fields such as quantum information,photonics and micro-nano electronics should be promoted with the country's strategic needs as the guide.Coherence and polarization,as two important degrees of freedom in the manipulation of light field,are widely used in the fields of quantum optics,micro-nano optics,particle acceleration,and optical information transmission.Vector partially coherent light fields have the properties of both partially coherent beams and vector beams,and they have crucial significance in advancing national strategy or improving people's livelihood and welfare.In this paper,we will introduce vector partially coherent light from two aspects of partial coherence and vector polarization,focusing on the measurement method of coherence structure,the fast algorithm and the three-dimensional polarization characteristics of tightly focused field.On one hand,optical coherence is an important property of light field,which has extremely high application value in optical communication,optical encryption and other fields.In recent years,with the development of the investigation into the coherence of beams,scientists have discovered that the coherence structure of partially coherent beams can describe in detail the correlation between the components of the wave light field at a pair of spatial points.Therefore,the importance of measuring the coherent structure of vector partially coherent light field is self-evident.The previous measurement methods still inevitably have shortcomings such as inefficient and incomplete.In this paper,a novel generalized Hanbury Brown–Twiss(HBT)experimental method is proposed.By introducing a pair of reference beams with rated phase difference and calculating the intensity correlation,the amplitude and phase information of the coherent structure of vector partially coherent light field can be measured efficiently.We have verified the accuracy of this method from theoretical and experimental aspects,and based on this method,the polarization state of vector partially coherent beam hidden behind the ground glass can be recovered.On the other hand,polarization is another important degree of freedom in the manipulation of light field.The vector light field with non-uniform polarization state distribution in space is widely used in quantum optics,micro-nano optics and other fields due to its peculiar tightly focused characteristics.The tightly focused characteristics of vector light field is usually quantified and studied by Richards-Wolf diffraction integral,but it is very difficult to directly integrate the cross spectral density function of vector partially coherent light field.In this paper,by rewriting the integral formula and decomposing the partially coherent light,a fast calculation algorithm of tightly focused field for vector partially coherent light field is proposed,which greatly improves the operation speed.Using this fast algorithm,we explored the threedimensional polarization characteristics of two kinds of vector beams in tightly focused field and found a lot of new phenomena.For example,radially polarized partially coherent Gaussian-Schell model beam can generate a nanoscale region around the focus where the field is essentially three-dimensional unpolarized;partially polarized dualmode superposition beams can produce an almost perfect nonregularity focal field at some locations.In addition,this paper also contains the summary of my work during my master's degree,and the planning and prospect of further investigation in the future.