Vortex Ultrashort Pulse Imaging Through Optical Parametric Amplification

The vortex light pulse is a wavefront phase a light field helical structure,because of its unique ring-shaped intensity distribution and carry the photon orbit determination of angular momentum,which has been widely used in optical micromanipulation,biomedical and quantum communication and other fields,has become an important branch of modern optics.With the rapid development of laser technology,especially in recent years,the development of ultra high power lasers,optical parametric amplification technology has also been rapid development.Since the 1990 s of last century,researchers have tried to apply optical parametric amplification to optical imaging.In the past twenty years,this research has been paid great attention both at home and abroad,and has made a lot of important research results.Because of its unique advantages,this imaging technique has been proved to have a broad application prospect in biology,medicine,physics,chemistry,military,national defense and other fields.This paper studies the vortex in optical parametric amplification applications in imaging,imaging is proposed by using the scheme of noncollinear optical parametric amplification of optical vortex pump,achieve high gain,high contrast and high spatial resolution of the optical parametric amplification of weak image imaging.The main research works are as follows:1.The basic theory of optical parametric amplification is studied.Analysis and discussion of the optical parametric amplification of nonlinear coupled wave equations,the phase matching method,the spatial walk off effect,by the numerical calculation and discussion of nonlinear optical crystals,the spectral bandwidth gain characteristics.These work provide a theoretical basis for high gain and high spatial resolution optical parametric amplification imaging.2.The basic characteristics of vortex beams and the filtering properties of spiral phase plates are studied.Analysis of the characteristics of the Hilbert transform the spiral phase plate,and set up a model of plane optical phase modulation spectrum 4f system,numerical simulation of the spiral phase plate filter imaging of amplitude and phase object respectively,compared the radial Hill Porter transform ordinary and shining effect on imaging of the fork shaped grating filter,found the shining fork grating filter can eliminate the side effect,improve the SNR of the imaging object.The theoretical basis is provided for parametric amplification imaging using spiral phase plate to produce vortex light.3.A scheme of non collinear optical parametric amplification imaging using vortex pumping is proposed.Simulated by noncollinear optical parametric amplification scheme of spectral imaging plane,first inserted in the pump light in the ordinary spiral phase plate on signal light phase filtering,high gain,high contrast and high spatial resolution optical image.Subsequently,the conventional helical phase plate is replaced by a class of Bessel spiral phase plates,which eliminates the side lobe effect and further improves the signal-to-noise ratio of the idle frequency optical image.