| This thesis is concentrated on the research of the properties of optical field as laser beam propagates through scattering media. The speckle field formed by the interaction of laser beam and scattering media is studied. The speckle phenomenon has been found for many years but has not been taken seriously due to the technology limitation at that time. With the rapid development of science and technology, especially the breakthrough and innovation in laser technology, the special laser beams have played most important role in modern optics technologies, which greatly promotes the research of the optical speckle, and this stimulates the interesting for studying the behaviors of the speckle produced by passing through the special laser beams through the scattering media.A speckle pattern will come into being under the effect of multiple scattering when laser beams pass through scattering media. If relevant information of speckle has been acquired, the image of reconstruction object would be accomplished, which is quite important to many scientific domains such as the modern biomedical imaging. Owing to being important of the speckle produced by passing laser beams through scattering media, in this thesis we focus on three aspects, listed as follows:First of all, we study the property of speckle field formed by vortex beams through scattering medium based on the theories of laser beam transmission theory and probability statistics. With unique vortex wave-front phase structure, fixed photon orbital angular momentum(OAM) and ring-shaped sectional light intensity, vortex beams are widely applied in numerous fields. Through theoretical analysis and experimental verification, It is found that as vortex beams pass through scattering media, the speckle property is influenced by topological charge of the vortex beams and the size of scattering medium.Secondly, we study the propagation characteristics of the azimuthally polarized non-diffracting beams(APB), and their propagation through the scattering medium. Based on the theoretical simulation, we also study the propagation characteristics of APB, and study the influence of the angle of the axicon for producing non-diffraction beam on the speckle. Moreover, we study the influence of polarization state of the light beams on the speckle. We experimentally set a Gaussian beam passing through a polarization converser to achieve the azimuthally polarized light beam, and the azimuthally polarized light beam is incident on a axicon to get APB. Then we discuss the speckle produced by passing APB through the scattering medium. It is found from the theoretical simulation that the speckle sizes will decrease as the decreasing of the size of the scattering medium, and size of the speckle will increase with the decreasing of the angle of the axicon for producing the non-diffraction beams.Finally, based on the principle of coherent diffractive imaging(CDI), we record the diffraction intensity which formed from laser beam through scattering medium, and retrieve the phase information by iterative algorithm. Then we can successfully retrieve the wavefront of scattering medium by the ptychographic iterative engine(PIE) imaging technique, which is an improved CDI method. We demonstrate light through scattering media for rebuilding the intensity and phase distribution. We realized imaging through scattering medium preliminary. The key advantage of PIE is that it has a wider view field, higher immunization capability to noise, and better convergence speed. Imaging through scattering materials may have great potential applications in biological imaging. |
