Optical Field Modulation And Imaging Of Laser Beam Passing Through Random Medium

Speckle can be observed in many optical fields.Due to the random scattering,a disordered speckle is generated when a laser beam passes through a scattering medium.Because of the mode coupling and superposition,imperfection,and dispersion et al.,the transmittance of light through a multimode fiber results in a speckle field as well.Such a disordered speckle affects the applications of laser beams.In this dissertation,the intensity and polarization of speckle field formed by multimode fiber,and the imaging of objects through ground glasses are studied.The contents are shown as follows:1.The transmittance of linearly polarized light through a multimode fiber generates a speckle in the exit end of the fiber.The randomness of the speckle is observed both in the intensity and polarization.Based on the feedback wavefront shaping technique,the intensity and the polarization of speckle is modulated.A focal spot is achieved via the iteration algorithm,and the polarization modulation is realized by employing the polarizer.Moreover,with the feedback of intensities from two detectors with polarizers,focal line with controllable polarization is accomplished.2.Deep learning is adopted to reconstruct the image of an object after passing through a scattering medium.The reconstruction by using Molilenet-based Unet is investigated,and it is demonstrated that speckle imaging can be realized with deep learning.The reconstruction with fewer label is accomplished by data enhancement.In addition,the reconstruction of polarized speckle field is compared.