Optical Field Manipulation Technique Applied To Singularity Optics

Singularity optic are considered as a new branch of modern optics.This kind of light field can maintain the existence of the optical singularity in the transmission process,and the existence of the optical singularity will lead to the zero light intensity of the singularity.The optical singularity refers to the point in the light field where the physical parameters cannot be defined.Therefore,the light intensity or amplitude of the point must be equal to zero to make it have physical existence.The phase singularity is the first and most widely studied object in the field of singularity optics.Unlike a beam that travels along a straight line,a vortex light is a light that spirals in the direction of its propagation,with a helical phase distribution.From the perspective of light fluctuation,the light of vortex moves forward spirally,so the phase of the central point in the position of continuous phase change makes the phase of the point uncertain,which leads to the disappearance of the amplitude of the field and the formation of dark field in the center of the light field,that is,zero light intensity.Polarization singularity is another kind of singularity of light field corresponding to phase singularity.The points with phase uncertainty due to the continuous change of phase are called phase singularities and the points with polarization uncertainty due to the continuous change of polarization are called polarization singularities.When we say polarization change,we usually mean the continuous change of linear polarization.A beam with a singularity of polarization is called a vector beam.Because of its unique optical characteristics,the singularity beam is of self-evident importance and has important application value in many fields.For example,particle capture,quantum manipulation,material processing,etc.,especially in the field of optical communication.The orthogonality is satisfied between the same kind of singular beams of different orders.For example,the vortices with different topological charges,the vector beams with different polarization topological charges,the laguerre gaussian modes with different topological charges or different radial coefficients,and the Hermitian gaussian modes with different orders are all orthogonal to each other.Therefore,both of them can be used as the carriers of module division multiplexing in optical communication and are important candidate technologies to realize the next generation high-capacity optical communication system.Modular division multiplexing,as the name implies,is the communication mode of each optical field mode as a channel on the same physical channel.In modular division multiplexing,it is necessary to adjust and control the plane light or the fundamental mode laser and transform it into the singularity beam of corresponding order.In order to realize the combination of multiple orthogonal singular beams,the singular beams can be transmitted on the same physical channel.Finally,it is necessary to adjust and control the mixed singularity beam so that the mixed singularity beam can be separated into individual beams,which is convenient for the next operation of the light field of each channel,namely pattern demultiplexing.At the same time,super fast and super strong singularity beam is also an important physical tool to study the physical process of strong field.However,because ultrafast laser contains rich spectrum,the generation of ultrafast and super strong singularity beam must be controlled by precise dispersion control.Therefore,in view of the above problems,this doctoral dissertation is dedicated to the research on the optical field regulation technology applied to singularity optics,mainly including the following aspects:1.Focusing on the topological load regulation of vortex beam,the vortex wave plate system with adjustable order based on liquid crystal was proposed for the first time.This novel vortex plate system has no mechanical parts and is a pure solid state electronic control system.The voltage configuration of the control system can achieve a wide range of order regulation.Here,we design a set of vortex wave plate system with 4 bit units,whose order adjustable range is-15~15,which can be used to generate order adjustable vortex light and vector beam,and the feasibility is successfully verified in the experiment.2.Dedicated to the study of ultra-fast femtosecond vortex pulse generation amplification technology.1)study the dispersion effect of vortex ultrashort pulse generation system based on vortex wave plate.Based on the Jones matrix,a new technique for improving the contrast of ultra-fast vortex light is proposed.2)a new super fast regeneration and amplification system of vortex light was proposed.By introducing a ring pump with adjustable radius,the system can effectively suppress the fundamental mode gaussian oscillation of the regenerated amplifier and stimulate the competition ability of the low-order laguerre gaussian mode.At the same time,an optical field similar to the low-order laguerre gaussian mode is injected and the high-power vortex pulse output is realized through the mode traction effect.Experimentally,the output 50.86 fs ultrafine vortex pulse energy reached 1.8 m J.3)in order to generate joule-scale femtosecond vortex,we used the quartz vortex plate system with high loss threshold to transform the ultra-strong femtosecond optical system.2.84 j and 20 fs femtosecond vortex pulses were successfully obtained experimentally.3.Aiming at the problem that the wavefront of vortex is unable to be recovered by traditional diffraction imaging technology,the rotational astigmatic diffraction imaging technology for recovering the wavefront of vortex is proposed.In this technique,rotating astigmatism is modulated by rotating cylindrical lens,and diffraction patterns distorted by different astigmatism angles are collected by camera.Taking these diffraction patterns as constraints,the amplitude distribution and phase distribution of the electric field can be reconstructed.The reconstruction resolution reached 14.25 lp/mm,equivalent to a diffraction limit of 0.6 times.At spatial frequency <4 mm-1,the phase reconstruction error is 138 mrad,or about ?/45.4.Aiming at the problem of efficient demultiplexing of vector light,1)The polarization topological load sorting technology based on polarization conjugate devices is proposed theoretically for the first time.By using polarization conjugate devices to focus the vector beams with different polarization topological charges to different positions,the decomposition function of polarization topological charges is realized,and the sorting efficiency can reach 78%.2)A polarization topological load sorting system based on geometric phase devices is proposed for the first time.The geometrical phase device based on optical orientation technology is designed and machined,and the feasibility of the system is verified through experiments.It is proved that the system can focus the vector beams with different polarizing topological charges to different positions,so as to realize the function of polarizing topological load decomposition,and the experimental sorting efficiency is up to 60%.3)A polarization topological load sorting system with high separation efficiency is proposed for the first time,which can introduce diffraction beam splitting into the polarization topological load sorting system based on geometric phase devices.Our experiments show that the separation efficiency of the polarization topological load demultiplexing system is improved from 58% to 78% by using the diffraction beam splitting method compared with the case without diffraction beam splitting.5.Aiming at the problem of using multiple diffractive phase plates to regulate the optical field,the optical diffraction neural network is studied theoretically,and three unavoidable laws in the optical diffraction neural network system are revealed.It is found that if the output light intensity is completely separated in space,the input light field must be orthogonal to each other.It can be seen that the optical diffraction network is suitable as a mode converter between two sets of orthogonal modes.In this case,there should be a one-to-one connection between the patterns.In this paper,we propose for the first time the use of optical neural network for the orthogonal mode(such as vortex)mode manipulation,and given for this kind of optical diffraction neural network system optimization design and algorithm.The ermi gauss-laguerre gaussian pattern converter,laguerre-gaussian demultiplexer and laguerre gaussian pattern recognizer are designed.The simulation results show that the optical diffraction neural network system performs well in the application of optically oriented orthogonal modes,such as pattern conversion,pattern multiplexer/sorter and optical pattern recognition,and can be used as an optical field manipulation means with high degrees of freedom.