Research On The Spot And Spatial Coherence Of The 46.9nm Laser Pumped By Capillary Discharge

The 46.9 nm soft X-ray laser pumped by capillary discharge is a kind of short-wavelength laser,which has many characteristics that ordinary wavelength laser does not have,such as high brightness,high coherence,high single-pulse energy and strong penetration.With the rapid development of laser pumped by capillary discharge,the 46.9 nm laser has a broad application prospect in such important fields as plasma diagnosis and nano-imaging.The neon-like argon laser has three wavelengths: 46.9 nm,69.8 nm and 72.6 nm.Among them,there are many researches on 46.9 nm laser in the world.In this thesis,the spatial characteristics of soft X-ray laser with a wavelength of 46.9 nm are studied from the aspects of theoretical numerical simulation and experiments,which include spatial intensity distribution of the spot and the spatial coherence.In terms of theoretical research,the propagation and amplification model of light in the plasma column is established.And numerical simulation of the spot intensity is carried out for different electron density distributions,which included four function electron density distribution,parabolic electron density distribution and multiple function electron density distribution.After that,the spatial distribution of laser spot intensity under different conditions was studied by modifying the parameters such as the gain distribution function and the maximum gain value.In the experimental research,the distribution of 46.9 nm laser spot intensity and the change of laser relative intensity under different argon pressure conditions were studied.And the distribution of electron density and gain in the plasma column under different conditions was preliminarily determined by comparing with the theoretical simulation results.On this basis,Young’s double slit is also used to study the fringe visibility of laser at different transverse positions of spots under different argon pressure conditions.At the same time,the maximum fringe visibility of laser under different argon pressure is studied.At last,the laser intensity distribution,relative intensity and fringe visibility of the laser are studied under different capillary lengths.In this thesis,the fringe visibility of laser is analyzed,and it is found that the fringe visibility of laser is closely related to the amplification process of laser transmission.That means,the more the laser amplification is,the better the fringe visibility is.The correlation between the fringe visibility and laser intensity is positive under the same condition.Through the simulation and experimental research of the spatial characteristics of the 46.9 nm laser pumped by the capillary discharge,the distribution of electron and gain in the plasma column under different laser intensity distributions can be understood.And the experimental conditions can be changed to obtain the laser output with good performance.By researching the fringe visibility of laser under different conditions,the factors affecting the fringe visibility can be understood.These results have a good guiding significance for laser with high gain and high spatial coherence,and also pave the way for the practical application of 46.9 nm laser.