铁电共振和非线性效应

Ferroelectric Resonance and Nonlinear Effect

本文基于质子—晶格耦合模型,采用分四套子格子描写质子系统,运用n+1时格林函数方法,讨论了KDP 型铁电晶体极化过程的线性和非线性效应.推导出二阶、三阶、四阶极化率能量.对线性效应;本文证明了沿c 轴纵向极化和沿a 轴横向极化两种情形的铁电共振频率分别为ω_(B±)(0)和ω_E(0);在居里温度以上时,静态纵向线性极化率遵从铁电居里一外斯定律,静态横向线性极化率遵从反铁电居里一外斯定律.对非线性效应;本文证明了纵向极化不能产生非线性效应,只有横向极化或横向和纵向同时极化才能产生非线性效应.对横向极化情形,在横向可产生奇数倍频,在纵向可产生偶数倍频.此外,在远红外范围内存在检波、混频、参放、泡克耳、克尔、受激拉曼等非线性效应。

The linear and nonlinear effect of Polarization Process in KDP type crystalsare discussed by the method of N+1 time Green's function based upon the model ofcoupling of the lattice with the proton system described as four sublattice.Thesecond-rank,third-rank,fourth-rank susceptibitity tensors are derived.For linear effect:it is proved that the ferroeleotric resonant frequencies oflongitudinal polarization along the C axis and transverse polarization along theA axis are respectively ω_(8±)(0)and ω_E(0).Above the transition temperature,thestatic longitudinal susceptlbility obeys the ferroelectric Curie-Weiss's law andthe static transverse susceptibitity obeys the antiferroelectric Curie-Weiss's law.For nonlinear effect:It is proved that the nonlinear effects can be resulted notfrom the longitudinal polarization,but from the transverse polarization or bothtransverse and longitudinal polarization.By the transverse polarizastion,the oddmutiplying frequency fields are generated in transvere direction and the even muti-plying frequency fields are generated in longitudinal direction.Besides,a numberof the nonlinear effects such as rectification,mixing.P(?)kels,Kerr,stimulated R-aman,etc,effects are existed in the far-infrared region,these effects are obviousespecially near the ferroelectric resonance.