Study On The Generation And Transmission Characteristics Of Broadband Ultrashort Vortex Pulses

The vortex beam is a special beam that exhibits a spiral phase and dark and hollow distribution during transmission.Because the vortex beam has a spiral phase factor and each photon carries orbital angular momentum,it exhibits unique properties in interaction with matter,free-space transmission,and nonlinear optics,so It has shown huge application prospects in the fields of multi-dimensional manipulation of particles,free-space optical communication,laser processing,etc.,and has received extensive attention and research in recent years.At present,it is one of the important research directions of vortex light to combine a vortex beam with a wide-spectrum short pulse to modulate the phase of the short pulse to generate a broadband ultra-short vortex pulse.The short pulse with vortex provides unprecedented research conditions and opportunities to many frontier fields of science,such as high-intensity field physics experiments,ultrafast nonlinear optics,precision laser material processing and other cutting-edge scientific fields.At the same time,the development of these fields has also put forward more and more new requirements for wide-spectrum ultrashort vortex pulses.The main work of the thesis has the following parts:1.This paper makes a brief introduction to the development history,application fields and common generation methods of vortex beams.2.Starting from Maxwell's equations,the mathematical expressions of the Hermite Gaussian beam and Laguerre Gaussian beam are derived,the principle of the mutual conversion of these two beams is essentially explained,and their light field distribution at the source plane is numerically simulated.The paper also introduces the interference method which one is the detection method of vortex light topological charge.The interference process of vortex light is numerically derived,and their interference patterns are also numerically simulated.3.The paper introduces seven kinds of broadband ultrashort vortex pulse generation schemes in detail,explains the principles of the key optical conversion elements,compares the advantages and disadvantages of each scheme,and designs a broadband ultrashort vortex pulse generation scheme based on CPA laser device.4.A physical model of Laguerre Gaussian beam propagation in free space was established,and the propagation process of Laguerre Gaussian beam in free space was numerically simulated.The spot change and phase distribution of Laguerre Gaussian beam in free space propagation were studied to compare the transmission characteristics of broadband ultrashort vortex pulses.5.Starting from Maxwell's equations,the physical model before and after the ultrashort pulse passes through the spiral phase plate is derived.Through numerical simulation,the pulse width expansion of the wide-spectrum ultrashort vortex pulse generated by the spiral phase plate and the distribution of light field during free space transmission were studied.This paper also designs related verification experiments.