Manipulation,statistics And Application Of Partially Coherent Beams In Spatial And Time Domain

Since the first laser came out in 1960,lasers have been widely used in many fields such as physics,chemistry,biology,medicine,industry,information technology,and national defense due to their unique properties.By properly controlling the inherent properties of the laser beam,many new physical properties could be found.Therefore,during recent years,light manipulation has gradually become one of the research hotspots in the field of optics.The previous methods of light manipulation are mainly limited to amplitude,phase,and polarization.Recent studies have shown that partial coherence beams can be obtained by reducing the coherence of a laser.By adjusting its degree of coherence,a series of novel and interesting physical characteristics can be triggered,which has broad application prospects in the fields of information encryption,optical communication,imaging and so on.In my thesis,we study the partially coherent beams in the spatial and time domains.The arrangements are given as firstly we have conducted in-depth research on the generation and propagation properties of scalar and vector spatially partially coherent beams.We choose the partially coherent beam with a non-Gaussian correlation as the source beam,whose intensity distribution possesses Gaussian or non-Gaussian shape.The evolutions of the beam intensity,degree of coherence and state of polarization in free space and through a thin lens focusing system are studied.We also study the influence of the source beam parameters on beam propagation properties in detail.The results show that under low coherence conditions,the far-zone intensity and state of polarization of the beam are determined by the source degree of coherence.The far-zone degree of coherence depends on the source intensity distribution.However,as the coherence increases,the beam properties under propagation will become more complex,and which will be determined by the source intensity and degree of coherence together.Secondly,we explore the application of the spatially partially coherent beams,and achieve that(1)the beam mode index of the vortex beam can be detected through measuring the degree of coherence.(2)we propose an optical system,which can generate various controllable array beams.(3)through controlling of the degree of coherence of the illumination source,we can improve imaging resolution and break through the Rayleigh diffraction limit.Finally,we study the statistical properties of time-domain partially coherent pulses in a nonlinear optical amplifiers.The results show that a Gaussian Schell-mode pulse,like a fully coherent Gaussian pulse,can generate a parabolic pulse and achieve self-similarity under propagation.For the pulse in the self-similar region,we study the statistical characteristics of the peak power of the pulse in the receiver plane.It is amazing to find that its probability density function also has self-similarity under propagation,and the optical rogue wave will be generated.In addition,we also study the effect of the source coherence on the statistical properties and optical rogue wave.We derive that as the source coherence decreases,the statistical characteristics of the peak power will change,and the probability and amplitude of the optical rogue wave will decrease accordingly.