掺杂KNSBN晶体吸收对光强的依赖特性

ENHANCED ELECTRON CYCLOTRON EMISSION DURING LOWER HYBRID WAVE DRIVE

研究了ＣｏＫＮＳＢＮ晶体和重还原ＣｏＫＮＳＢＮ晶体中光致吸收的变化特性。ＣｏＫＮＳＢＮ晶体的吸收系数随泵浦光强的增加而减小，吸收系数变化的最大值为３．２ｃｍ－１，重还原ＣｏＫＮＳ－ＢＮ晶体的吸收系数随泵浦光强的增加而增加，吸收系数变化的最大值为６．５ｃｍ－１，在泵浦光关掉后，探测光频率很高的增幅振荡，然后呈现阻尼振荡。采用最近建立的双载流子（电子，空穴）和多重陷阱能级（两个深陷阱能级，两个浅陷阱能级）的光折变理论给以合理的解释，同时指出晶体的光致吸收变化特性在获得空间均匀光和非相干光放大中，有着潜在的应用。

High frequency electromagnetic radiation driven by lower hybrid wave is studiedbased on three wave (the hybrid wave, high frequency electrostatic wave and electromagnetic wave) resonant interaction. The guiding center formalism of Vlasov equation is followed to obtain the nonlinear coupling coefficients including kinetic effects. Velocity space integrals in the coupling coefficients are strictly performed in small k z  approximation. General nonlinear dispersion relations of the parametric instability are obtained. Analytical analysis indicates that: (1) due to kinetic coupling effects, lower hybrid wave can excite electron Bernstein wave accompanied by high frequency electromagnetic wave; (2) the elctromagnectic radiation driven in this manner is thermal electron cyclotron radiation, and the intensity of the radiation is enhanced when increasing the plasma temperature and density. It is consistent with most experimental observations. This suggests that the present instability can be responsible for the enhanced electron cyclotron emission during lower hybrid wave drive and be regarded as the origin of the electron cyclotron emission in the plasma.