弱耗散磁调谐稠密随机介质：铁磁流体的光散射
Light scattering from a magnetically tunable dense random medium with weak dissipation : ferrofluid
摘要：
我们提出了一个半唯象处理光透射和反射的铁磁流体，我们认为这是一个磁可调系统的密集随机介质散射弱耗散。部分空间有序是通过施加横向磁场来引入的，该横向磁场在介电随机性上叠加了周期性调制。这引入了布拉格散射，其有效地增强了仅由于无序引起的散射，并且因此减小了朝向安德森局域化的弹性平均自由程。我们的理论治疗，不变的嵌入的基础上，给出了一个同时减少的透射和反射，而不改变入射线偏振的空间秩序是磁性调谐到布拉格条件，即光波矢量等于一半的布拉格矢量（Q）。我们的实验观察与这些结果定性一致。我们还给出了光的渡越（逗留）时间和在稳定照明下储存在随机介质中的光能的表达式。因此，铁磁流体提供了一个有趣的物理实现有效的“有损耗的安德森-布拉格”（LAB）腔与研究的空间无序，偏序和弱耗散光传输的相互作用的效果。鉴于目前的兴趣在传播，光限幅和存储的光在铁磁流体，目前的工作似乎热门。
英文摘要：
We present a semi-phenomenological treatment of light transmission through and its reflection from a ferrofluid, which we regard as a magnetically tunable system of dense random dielectric scatterers with weak dissipation. Partial spatial ordering is introduced by the application of a transverse magnetic field that superimposes a periodic modulation on the dielectric randomess. This introduces Bragg scattering which effectively enhances the scattering due to disorder alone, and thus reduces the elastic mean free path towards Anderson localization. Our theoretical treatment, based on invariant imbedding, gives a simultaneous decrease of transmission and reflection without change of incident linear polarisation as the spatial order is tuned magnetically to the Bragg condition, namely the light wave vector being equal to half the Bragg vector (Q). Our experimental observations are in qualitative agreement with these results. We have also given expressions for the transit (sojourn) time of light and for the light energy stored in the random medium under steady illumination. The ferrofluid thus provides an interesting physical realization of effectively a "Lossy Anderson-Bragg" (LAB) cavity with which to study the effect of the interplay of spatial disorder, partial order and weak dissipation on light transport. Given the current interest in propagation, optical limiting and storage of light in ferrofluids, the present work seems topical.
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