First-principles Study Of Terahertz Band Nonlinear Optical Crystal Gallium Selenide

The unique properties of terahertz wave brought a profound impact in the field ofcommunication, radar, electronic countermeasures, electromagnetic weapons, astronomy, medicalimaging, non-destructive testing and safety inspection. Among many methods to generate terahertzwave, by use of the nonlinear crystal nonlinear conversion seems more streamlined, inexpensive,and has the same tonality terahertz light. Therefore, looking for the excellent performance of thenew terahertz nonlinear optical crystal materials has become one of the current difficulties in thefield of non-linear optical materials research and cutting-edge direction. If we could find aexcellent nonlinear optical crystal material to generate terahertz waves that have undoubtedly greatsignificance to the promotion of terahertz wave technology.By using the first-principles calculation based on density functional theory, and the CASTEPmodule in Materials Studio software, this paper study the electronic structure, optical and elasticproperties of ideal GaSe single crystal, electronic structure and optical properties of GaSe crystalwith intrinsic defects, as well as the elasticity and electronic structure performance of GaSe crystalmixed with S, In, Te, Cu and Zn.Firstly, study the electronic structure properties of GaSe crystal by calculating the bandstructure, total density of states, partial density of states and the differential charge density of idealGaSe single crystal; calculate the imaginary part of the dielectric function, energy loss function,index of refraction, reflection and absorption rate, we can know the optical properties of GaSecrystal; then the elastic properties of GaSe crystal were calculated and analyzed, especially withchanges in external pressure when the external pressure from0GPa to35GPa.Secondly, we carry out a performance study of the intrinsic defects of GaSe crystal, includeelectronic structure and optical properties. Study the influence of intrinsic defects on the nature oselectronic structure of GaSe crystal by learn the different defect density distribution; calculate theimaginary part of the dielectric function, energy loss function, index of refraction, reflection andabsorption rate, study the optical properties of GaSe crystal.Finally, research the elastic properties of GaSe: X (X=S, In, Te, Cu and Zn) crystal, singledoped concentration is0.25mol%,0.125mol%,0.0625mol%, respectively. According to the analysis of the elastic properties of crystal, study the electronic structure of GaSe: X crystalsdeeply by the density of states of the doped crystals.