We use non-resonant Raman scattering to demonstrate a large enhancement of the effective refractive index experienced by Raman photons in a scattering medium comprising spatially-correlated photonic structures of core–shell TiO₂@Silica scatterers mixed with silica nanoparticles and suspended in ethanol. We show that the high refractive index extends outside the physical boundary of the medium, which is attributed to the evanescent contributions of electromagnetic modes that are strongly localized within the medium. Notably, the effective enhancement can be observed even at very low intensities of Raman emission. This anomalous non-linear phenomenon could be explained by the successive polarization of valence electrons to virtual states induced by the strong photon correlations in the strongly localized electromagnetic modes. The enhancement of refractive index and its extension in the vicinity of the medium's interface provide new opportunities for controlling the electromagnetic fields in advanced photonic devices.

中文翻译：

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强烈增强结构化胶体中的有效折射率 （TiO2@Silica）


我们使用非共振拉曼散射来证明拉曼光子在散射介质中的有效折射率大大增强，该散射介质由核壳TiO2@Silica散射体的空间相关光子结构与二氧化硅纳米颗粒混合并悬浮在乙醇中。我们表明，高折射率延伸到介质的物理边界之外，这归因于在介质中强烈定位的电磁模式的倏逝贡献。值得注意的是，即使在非常低的拉曼发射强度下也可以观察到有效的增强。这种反常的非线性现象可以用强局域电磁模式中的强光子相关性引起的价电子连续极化为虚拟状态来解释。折射率的增强及其在介质界面附近的延伸为控制先进光子器件中的电磁场提供了新的机会。