Abstract Raman spectroscopy allows nondestructive analysis of materials using laser illumination. However, most Raman spectrometers can only provide good signal levels and sufficient spectral resolution, by focusing the laser to micrometer-sized spots. This equates to enormous laser intensities, which for samples with even very minor optical absorption either means destroying or damaging it by absorbing even a tiny fraction of the laser power, or it means reducing the laser intensity and hence the signal level. Furthermore, Raman signals generated above or below the focal plane are rejected in traditional Raman spectrometers. As signal levels are already extremely low in Raman spectroscopy, several schemes offer an alternative to focusing down to a diffraction-limited spot, to increase the area by up to 6 orders of magnitude, and increase the sampling depth. This review describes and compares these schemes, and estimates the typical illumination areas.

中文翻译：

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广域拉曼光谱

摘要 拉曼光谱允许使用激光照明对材料进行无损分析。然而，大多数拉曼光谱仪只能通过将激光聚焦到微米大小的点来提供良好的信号水平和足够的光谱分辨率。这相当于巨大的激光强度，对于光吸收非常小的样品来说，这意味着通过吸收甚至很小一部分激光功率来破坏或损坏它，或者意味着降低激光强度，从而降低信号水平。此外，在焦平面上方或下方生成的拉曼信号在传统拉曼光谱仪中被拒绝。由于拉曼光谱中的信号水平已经非常低，因此有几种方案提供了一种替代方法来聚焦到衍射极限点，将面积增加多达 6 个数量级，并增加采样深度。本综述描述和比较了这些方案，并估计了典型的照明区域。