Theoretical Study On Diode Pumped Nanoparticle Gas Laser

Nanoparticles are one of the attractive building blocks for nanotechnology,and they offer new possibilities for novel lasers.The rare earth doped nanoparticle gas laser inherently combines the advantages of the solid state laser and gas laser,including all-electric drive,compact configuration and efficient heat management.This idea provides unlimited potential for the high energy laser,and it becomes a new approach for the megawatt-class laser with all-electric drive of next generation.Until now,only three patents have introduced preliminary descriptions of this concept,but they lack further theoretical investigation.For this reason,we carry out the preliminary theoretical research of this new concept.1.The development course of high energy laser and the enlightenment of it are reviewed briefly,and the law behind it shows that the diode pumped nanoparticle gas laser?DPNGL?conforms the trend of high energy laser.Also,the definition of DPNGL and its advantages are summarized.2.A rate equation model of Yb³⁺doped DPNGL is established.The model includes special considerations of the scattering influence of nanoparticles,and the modifications of Yb³⁺fluorescence lifetime as well as the cross sections,which distinguishes it from the traditional lasers.Some main influencing factors are simulated and discussed,including the Yb³⁺concentration,gain length and the output coupler etc.,and the energy conversion channels of absorbed pump power are analyzed.The results predict a slope efficiency of greater than 60%and threshold pump density less than 4kW/cm² at reasonable conditions.The highest slope efficiency is up to 80%.Meanwhile,the scientific issues concerning the DPNGL are summrized,and their possible sloutions are proposed as well.3.Based on the density functional theory,different Yb³⁺doping level of Y₃Al₅O₁₂?YAG?and YAlO₃?YAP?crystals are calculated from the first-principles.These results will provide standards for the first-principles calculation of nanocluster and nanoparticle.According to the results,the conduct band is dominated by 4d states of Y,and the valence band is dominated by oxygen 2p states in the these two types of crystals with different Yb³⁺concentration.Due to the poor description of 4f electrons by PBE functional,the Yb p states contribute to a impurity state.The bandgap increases with the rise of doping level of Yb³⁺ions.The absorption spectrums of Yb³⁺doped YAG crystals show a blue shift,and some structures are anisotropic.The anisotropic absorption spectrums of YAP crystals in the range of 0-500 nm remain the same,while the intensity of them increases greatly in the range of 500-3000 nm when the Yb³⁺concentration increases.4.The common methods and softwares of cluster structure prediction are introduced briefly.Based on the potential field,the?Yb₂O₃?_n?n=2-9?clusters are studied.According to the results,the structures tend to exhibit high symmetry when the clusters are relatively small,and the isomers of them have small relative energy gaps.When the cluster becomes larger,except the Yb₁₆O₂₄ cluster resembles a sphere,the most stable structures tend to be triangular pyramids.