Zhu Yifan, Ge Xiaowei, Ni Hongli, Yin Jiaze, Lin Haonan, Wang Le, Tan Yuying, Prabhu Dessai Chinmyee Vallabh, Li Yueming, Teng Xinyan, Cheng Ji-Xin
bioRxiv. 2023 Sep 7:2023.03.06.531387. doi: 10.1101/2023.03.06.531387.
Stimulated Raman scattering (SRS) microscopy has shown enormous potential in revealing molecular structures, dynamics and coupling in a complex system. However, the bond-detection sensitivity of SRS microscopy is fundamentally limited to milli-molar level due to the shot noise and the small modulation depth in either pump or Stokes beam4. Here, to overcome this barrier, we revisit SRS from the perspective of energy deposition. The SRS process pumps molecules to their vibrational excited states. The thereafter relaxation heats up the surrounding and induces a change in refractive index. By probing the refractive index change with a continuous wave beam, we introduce stimulated Raman photothermal (SRP) microscopy, where a >500-fold boost of modulation depth is achieved on dimethyl sulfide with conserved average power. Versatile applications of SRP microscopy on viral particles, cells, and tissues are demonstrated. With much improved signal to noise ratio compared to SRS, SRP microscopy opens a new way to perform vibrational spectroscopic imaging with ultrahigh sensitivity and minimal water absorption.
受激拉曼散射（SRS）显微镜在揭示复杂系统中的分子结构、动力学和耦合方面已显示出巨大潜力。然而，由于散粒噪声以及泵浦光束或斯托克斯光束中的小调制深度，SRS显微镜的键检测灵敏度从根本上限制在毫摩尔水平。在此，为克服这一障碍，我们从能量沉积的角度重新审视SRS。SRS过程将分子泵浦到其振动激发态。随后的弛豫使周围环境升温并引起折射率变化。通过用连续波光束探测折射率变化，我们引入了受激拉曼光热（SRP）显微镜，在保持平均功率不变的情况下，对二甲基硫实现了>500倍的调制深度提升。展示了SRP显微镜在病毒颗粒、细胞和组织上的多种应用。与SRS相比，SRP显微镜具有大大提高的信噪比，为以超高灵敏度和最小水吸收进行振动光谱成像开辟了一条新途径。
