In this work, we tackle the problem of the spatially selective optical excitation of spin dynamics in structures with multiple magnetic layers. The 120 fs circularly polarized laser pulses were used to launch magnetization precession in an all-dielectric magneto-photonic crystals (MPC) formed by magnetic layers sandwiched between and inside two magnetic Bragg mirrors. Optical pump-probe experiments reveal magnetization precession triggered via ultrafast inverse Faraday effect with an amplitude strongly dependent on the pump central wavelength: maxima of the amplitude are achieved for the wavelength tuned at the cavity resonance and at the edge of the photonic bandgap. The optical impact on the spins caused by the inverse Faraday effect and spectrum of this effect are found to correlate mostly to the direct Faraday effect. We show that even though the pump laser pulses propagate along the whole structure tuning their wavelength allows localization of a larger spin precession either in the cavity layer or in the Bragg mirror layers selectively. The results pave the way to the ultrafast optical control of magnetization dynamics at a sub-wavelength scale that is vital for modern magneto-photonics and magnonics.

中文翻译：

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光谱可调超短激光脉冲对磁光子晶体自旋动力学的空间选择性激发

在这项工作中，我们解决了具有多个磁性层的结构中自旋动力学的空间选择性光学激发问题。120 fs 圆偏振激光脉冲用于在由夹在两个磁性布拉格镜之间和内部的磁性层形成的全电介质磁光子晶体 (MPC) 中发射磁化进动。光泵浦探针实验揭示了通过超快反法拉第效应触发的磁化进动，其幅度强烈依赖于泵浦中心波长：在腔谐振和光子带隙边缘调谐的波长达到幅度的最大值。发现由逆法拉第效应和该效应的光谱引起的对自旋的光学影响主要与直接法拉第效应相关。我们表明，即使泵浦激光脉冲沿着整个结构传播，调整它们的波长也允许在腔层或布拉格镜层中选择性地定位更大的自旋进动。这些结果为在亚波长尺度上对磁化动力学进行超快光学控制铺平了道路，这对于现代磁光子学和磁子学至关重要。