Research Of Light-assisted Domain In-Version On Mg-doped Lithium Niobate Crystals

Quasi-phase matching(QPM)technology is one of the most effective ways to achieve high-efficiency laser nonlinear frequency conversion.The key of achieving QMP is the nonlinear crystal with periodic polarization.Light-assisted domain inversion technology for periodically polarized lithium niobate(PPLN)can overcome the shortcomings of the electric field polarization method commonly used nowadays.This thesis mainly focuses on the foundation and engineering research of light-assisted domain inversion technology combined with the laser direct writing technique to obtain inverting domain in the specified area on magnesium-doped lithium niobate(Mg:LN)crystal.We analyzed ferroelectric effect,piezoelectric effect and related optical characteristics of LN and showed the process of domain polarization reversal of LN under external electric field.The physical mechanism of domain polarization reversal of Mg:LN crystals based on the generation and transport of photo-excited carriers was discussed.We set up an experimental system using 532 nm continuous laser to realize the domain polarization inversion structure on Mg:LN by laser direct writing,meanwhile we can observe the structure in real-time with this system.Inversion quality and inversion characteristics under different experimental conditions was studied,which may lay a foundation for the flexible preparation of domain inversion devices.