飞秒光诱导铽镓石榴石晶体中的磁化响应研究

Femtosecond photoinduced magnetization of terbium gallium garnet crystal

运用时间分辨抽运-探测光谱技术,研究了磁光晶体铽镓石榴石(TGG)在不同椭圆偏振态的飞秒激光脉冲诱导下的极化和磁化响应.研究表明,当仅存在逆法拉第效应时,探测光旋转角信号和椭圆率信号的变化方向与圆偏振抽运光的旋向相关.这是由于圆偏振光在TGG晶体中产生的瞬态有效磁场的方向依赖于圆偏振光的旋向所致.光诱导磁化过程与材料的性质有关,TGG晶体的顺磁特性决定了其自旋弛豫时间为几十飞秒.由于探测光旋转角信号和椭圆率信号的半高全宽均为500fs左右,加之信号强度随着抽运光脉冲能量密度的增加呈线性增长,表明TGG晶体有望成为超快全光磁开关的候选材料.

The photoinduced magnetization in magneto-optical crystal terbium gallium garnet （TGG） is investigated by time-resolved pump-probe spectroscopy.When the pump pulse is elliptically polarized,the rotation signal and the ellipticity signal of the probe pulse are observed at zero time delay,resulting from the optical Kerr effect and the inverse Faraday effect.The direction of the effective magnetic field is dominated by the helicity of the pump pulse,so the rotation signal and the ellipticity signal of the probe pulse can be triggered selectively by modifying the helicity of the pump pulse.The full widths at half maximum of the rotation signal and the ellipticity signal both can be as fast as about 500 fs,which indicates that TGG crystal is expected to be a candidate material of ultrafast all-optical magnetic switching.