Study On The Generation And Propagation Of New-type Beam By Spatial Light Modulator

The related studies of modulating light fields have always been a hot spot in modern optics,including the amplitude,phase,coherence,polarization and other properties of light field.The traditional way of studying light fields is limited to numerical simulation based on the diffraction integral formula,while the experiment is lacking.In experiments,fixed elements such as lens,polarizers,and q-plates are usually used to change the properties of the light field,which can easily make the experimental device complicated.The spatial light modulator is a new type of diffractive optical element,which has the advantages of high resolution-nominal,nice programmability,high fill factor,and high diffraction efficiency.It can be used to modulate the phase and the amplitude of the light field in optical experiment.In recent years,experimental research in optical modulation has been more and more important with the widespread use of spatial light modulators,and the functions of the spatial light modulator have also been developed a lot.On the basis of the basic functions of the spatial light modulator,more advanced experimental methods gradually appear such as generating partially coherent beams and simulating turbulent environment,which greatly promote the development of experimental optics.Based on this background,we mainly use the spatial light modulator to carry out experimental research on generation and propagation of new-type beam in the dissertation,including the spectral density of vortex beams propagating in turbulence,the effect of new twisting phase on beams,the experimental generation and the transmission characteristics of partially coherent beams.The specific chapters in this paper are arranged as follows:In the first chapter,we introduce the background of all studies in this paper,including the vortex beams,the theory of partially coherent beams,the history of turbulence,the twisted beams and the new twisting beams.After that,the main theoretical basis and research methods required in this paper are introduced,including generalized diffraction integral formula,cross spectral density function,turbulent power spectral density model and fractional Fourier transform.Finally,the principle of the spatial light modulator is introduced,which lays the foundation for the experimental part of the whole paper,pointing out the research topics.In the second chapter,we study the spectral density of vortex beams propagating in atmospheric and oceanic turbulence by both numerical simulation and experiment.The experimental part is based on the spatial light modulator.By loading the random phase graph,the effect of turbulence on the phase of the light field is simulated in the laboratory.The theoretical part is based on the diffraction integral formula of optical diffraction and added the modification like beam wander.By adjusting the relevant parameters in the turbulent power spectral density model,the influence of the turbulence on the vortex beam was studied,and consistent results were obtained from both numerical simulation and optical experiment.In chapter 3,we introduce the effect of the new twisting phase,which is similar to the twisted phase.The new twisting phase is introduced into the anisotropic Gaussian beam to study the spectral density during propagation and analyze the effect of the new twisting phase.In experiment,by loading the phase graph of the new twisting phase on SLM,the required beam can be obtained from the first-order reflected beam.According to numerical simulation and optical experiment,a flip theory is proposed to describe the rotation phenomenon caused by the new twisting phase,which could analyze the effect of the new twisting phase better.In chapter 4,we study the experimental generation and transmission characteristics of partially coherent beams,mainly including two parts.The first one is extending the transmission of vortex beams in turbulence to the field of partially coherent beams.The spectral density of partially coherent vortex beams propagating in atmospheric turbulence is studied,where the partially coherent beams is generated by the window function method using a spatial light modulator.The other content is that the new twisting phase is introduced into the partially coherent beam.A kind of reversal rotating beam is proposed and its transmission characteristics are studied where the partially coherent beam is generated by a rotating ground-glass disk.Through numerical simulation and optical experiment,the properties of partially coherent beams are studied.In chapter 5,we summarize the main work and innovations introduced in this paper,and put forward the prospects for planned work in future.