Study On Digital Holographic Diffractive Imaging And Its Applications In Polarization Measurement And Ultrafast Imaging

In recent years,along with the deep research on ultrafast laser and laser-matter interaction,how to real-time observe and characterize the evolution of an ultrafast vector beam and the polarization related micro structural formation induced by ultrafast laser has become an important issue.Digital holographic diffractive imaging technology is an impotant method for imaging and measuring objects in optical field.It also can be used in researching the polarization measurement and ultrafast phenomena imaging.This dissertation focuses on new digital holographic diffraction imaging methods,especially the polarization measurement and ultra-fast imaging technology based on digital holographic diffraction imaging.The main contents of the dissertation are as follows:1.The research background and progress of digital holographic diffractive imaging are reviewed.The development of ultrafast lasers and their applications in interaction with matter are briefly introduced.At the same time,some polarization measurement methods and ultra-fast imaging methods are introduced in detail,pointing out the advantages and disadvantages of various methods and the problems that need to be solved in current research.2.The basic theories of digital holographic diffractive imaging and polarization measurement are summarized.They mainly includes the principle of holographic recording and reconstruction,the scalar diffraction theory of light propagation in space,the sampling theorem and the Babinet principle,as well as the Jones matrix theories describing polarized light and birefringence characteristics of anisotropic materials.3.A lensless digital holographic diffractive imaging method based on complementary random sampling is proposed and studied.The main innovations of this research are as followings.Firtly,a set of complementary binary random sampling screens(CRS screens)is introduced,which is placed between the measured object and the recording plane in turn.Secondly,the diffraction intensity patterns of the object wave passing through the sampling screen are respectively recorded at the recording plane in turn.Thirdly an inventive complementary sampling retrieval algorithm is used to retrieve the complex amplitude(includes the amplitude and phase)distributions of the object wave from the recorded intensity patterns.Finally,by using the recovered complex amplitude distribution,the diffraction image of the measured object at any position in space can be obtained through a digital diffraction operation.The theoretical and experimental results show that the method greatly improves the accuracy and iteration efficiency of the complex amplitude retrieval by inserting the CRS screen between the object and the recording plan.At the same time,the influence of the random sampling on the sieved field can be well eliminated.In addition,because the iteration process in this method is only applied between the sampling plane and the recording plane,it can be applied to more general complex valued objects without proper constraints.4.An ultra-fast time-resolved multi-channel polarization holographic microscopic imaging method and experimental system based on femtosecond or picosecond ultra-short pulsed laser are proposed and studied.Compared with other ultra-fast time-resolved imaging techniques,the most advantage of this method is that it retrieve and image the amplitude and the phase distributions of two orthogonal polarization states of an ultrafast event at two different times(with ultra-short time interval)in one-shot measurement.Based on this system,we characterize the ultrafast processes in two typical polarization sensitive materials(linear polarizers and mica plates),and successfully observe the generation and propagation of shock waves in experiments.This technique provides a new and effective way to characterize the ultrafast process in polarization sensitive materials.This study lays a theoretical and experimental foundation for the further development of a new ultra-fast time-resolved multi-channel polarization holographic microscope matching with femtosecond or picosecond pulsed laser system.5.A method of four-channel Jones matrix measurement based on ultra-fast laser is proposed and studied.A four-channel angular multiplexing hologram can be obtained by a single shot.The Jones matrix information of the polarization sensitive sample to be measured can be easily retrieved from the spatial spectrum of the hologram.The feasibility of this method is proved by measuring the Jones matrix of starch granules in microfluidic chips and the polarization of liquid crystals at different voltages.In addition,when we change the picosecond laser to femtosecond laser,as long as the time interval between two detection pulses is larger than the pulse width,the recording requirements can be satisfied,thus realizing the real-time Jones matrix measurement of femtosecond dynamic process.6.An experimental system and method for realizing 2D single-shot measurements of birefringence parameters(both including the retardation and optic axis orientation)of anisotropic materials using a simple recording setup and an efficient processing algorithm is proposed and studied.The recording setup can be built simply by inserting a circular polarizer and an acute polarization beam splitter,respectively,in the object path and the reference path of a conventional off-axis holographic imaging system,with no need of other adjustments.At the same time,an algorithm for quantitatively retrieving the birefringence parameters from one single-shot hologram is proposed and demonstrated,in which a new quantity describing the birefringence,called complex birefringence parameter,is introduced,and a set of formula used to extract the birefringence parameters is derived.Furthermore,a formula is given for extracting the birefringent phase delay parameters and the optical axis orientation parameters from the complex birefringence parameters.Some experimental results are given for demonstrating the feasibility of the method,which reveals that the method may provide another effective approach for investigating the birefringence properties of dynamic anisotropic materials,especially the birefringence induced by ultrafast pulse lasers.