SGER: Detection of Optical Absorption from Individual Molecules Using Sagnac Interferometry

斯坦福大学的William E. Moerner和Martin M. Fejer教授得到了分析和表面化学以及原子和分子光学项目的支持，利用光学吸收和Sagnac干涉仪检测单个分子。这项探索性研究小额资助的想法是避免对荧光的依赖，而荧光是目前大多数单分子光谱学的基础。吸收将是一种更全面的方法，但由于高背景噪声，通常不那么敏感。Sagnac干涉测量法直接测量光束在环中顺时针和逆时针运动时所经历的光学相移的差异。它对探测激光产生的过量相位幅值和相位噪声不敏感。利用二次脉冲激光对分子吸收进行饱和调制，使分子吸收随时间变化。通过扫描探测激光的探测体积在样品上，可以生成超细微特征的显微图像。该项目有可能影响几个领域，包括痕量检测、生物物理学、材料科学、量子信息和纳米科学。例如，在生物细胞中，可以在没有染料标签的情况下进行单分子光谱分析，因为染料标签可能会干扰系统，也不会受到虚假发射器的干扰。

Professors William E. Moerner and Martin M. Fejer of Stanford University are supported by the Analytical and Surface Chemistry and Atomic and Molecular Optics Programs to detect individual molecules using optical absorption and a Sagnac interferometer. The idea of this Small Grant for Exploratory Research is to avoid the dependence on fluorescence, which is the basis of most single molecule spectroscopy at present. Absorption would be a much more global approach, but is usually not as sensitive due to high background noise. Sagnac interferometry directly measures the difference in optical phase shift experienced by beams traveling clockwise versus counterclockwise in a ring. It is insensitive to excess phase amplitude and phase noise from the probing laser. Saturation modulation of the molecular absorption with a secondary pulsed laser will be used to make the molecular absorption time varying. By scanning the detection volume of the probe laser over the sample, microscopic images of ultrasmall features can be generated. The project has the potential to impact several fields including trace detection, biophysics, materials science, quantum information and nanoscience. In biological cells, for example, it would be possible to perform single molecule spectroscopy without dye labels, which potentially perturb the system, and without interference from spurious emitters.