Min Wei, Gao Xin
Department of Chemistry, Columbia University, New York, NY 10027, USA.
Sci Adv. 2024 Dec 13;10(50):eadm8424. doi: 10.1126/sciadv.adm8424. Epub 2024 Dec 11.
The advent of stimulated Raman scattering (SRS) microscopy has launched a rapidly growing field in chemical imaging with broad impact. Although the physical picture seems to be well understood from classical models, prediction of absolute SRS signals remains a challenge. Here, we present a quantum electrodynamics treatment of the newly introduced stimulated Raman cross section. The resulting formula for calculating the absolute SRS signal is simple and differs from the commonly used relations by only one factor. We demonstrate the utility of this formula in a broad range of crucial applications of SRS microscopy, including stimulated Raman enhancement factor (>10 times), signal-to-noise ratio (SNR) of typical imaging experiments, population saturation under high power excitation, and energy deposition during stimulated Raman photothermal microscopy. In particular, the theory predicts that SRS microscopy is almost always more sensitive than spontaneous Raman microscopy for chemical imaging.
受激拉曼散射（SRS）显微镜的出现开创了一个快速发展的化学成像领域，具有广泛影响。尽管从经典模型来看物理图像似乎已被很好地理解，但预测绝对SRS信号仍然是一个挑战。在此，我们对新引入的受激拉曼截面进行了量子电动力学处理。所得用于计算绝对SRS信号的公式很简单，与常用关系仅相差一个因子。我们在SRS显微镜的一系列关键应用中展示了该公式的实用性，包括受激拉曼增强因子（>10倍）、典型成像实验的信噪比（SNR）、高功率激发下的粒子数饱和以及受激拉曼光热显微镜中的能量沉积。特别是，该理论预测在化学成像方面，SRS显微镜几乎总是比自发拉曼显微镜更灵敏。
