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

斯坦福大学的William E.Moerner教授和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，他们利用光学吸收和Sagnac干涉仪来检测单个分子。这个探索性研究的小资助金的想法是为了避免对荧光的依赖，这是目前大多数单分子光谱学的基础。吸收是一种更具全局性的方法，但由于背景噪声较高，通常不那么敏感。Sagnac干涉术直接测量环形中顺时针和逆时针方向的光束所经历的光学相移的差异。它对探测激光过多的位相幅度和位相噪声不敏感。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。通过在样品上扫描探测激光的探测体积，可以生成超微小特征的显微图像。该项目有可能影响多个领域，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，可以在没有染料标记的情况下进行单分子光谱分析，这可能会扰乱系统，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.