磁场对周期性极化铌酸锂晶体中产生的窄带太赫兹波的控制研究

Magnetic field modulation on narrowband terahertz wave in photorefractive periodically poled lithium niobate crystal

本文利用飞秒激光作用于光折变周期性极化铌酸锂(PPLN)晶体和掺镁(Mg)的PPLN(PPMg:LN)晶体通过光整流效应产生窄带太赫兹(THz)辐射,通过外加磁场的办法对THz脉冲串的振幅和寿命进行有效控制。随着外加磁场的增强,在光折变PPLN晶体中产生的THz波的振幅和寿命都随之减小;当外加磁场足够强时,光折变PPLN晶体中产生的THz波将完全被抑制。外加磁场之所以能够对THz波的振幅和寿命进行有效控制,主要是由于洛伦兹力的作用使光折变晶体内部产生了空间电荷场。

The generation and detection of narrowband terahertz （THz） wave based on photorefractive periodically poled lithium niobate （PPLN） and periodically poled Mg：LiNb3（PP-Mg：LN） crystal are realized by optical recti fication.By changing the size and direction of the applied magnetic field,the effective mod ulation on the amplitude of the narrowband THz wave is achienved in photorefractive PPLN crysta l.With the increase of the applied magnetic field,the amplitude of narrowband THz wave in the photorefractive PPLN crystal is supressed. When the applied magnetic field is sufficiently strong,narrowband THz wave in t he photorefractive PPLN crystal can be completely suppressed.For PP-Mg：LN cryst al,a completely different phenomenon of the THz wave is observ ed.The oscillation of the generated THz wave does not produce any changes,either with or without the magnetic field.The magnetic field modulation of THz wave in the photorefractive PPLN crystal comes from the buildup of a space-charge fiel d through Lorentz force.