Research Starter Grant: Three-Dimensional Polarization Second-Harmonic Generation Microscopy

伊利诺伊大学厄巴纳-香槟分校的Toussaint博士获得了一项资助，用于开发三维偏振二次谐波产生显微镜。这种方法是传统荧光显微镜的一种替代方法，使用非线性光学散射完全避免了对外源探针的任何依赖，而是使用所研究标本的化学性质作为造影剂，从而允许真正的无创成像。这里的警告是，SHG显微镜适用于一种特殊的，但非常相关的生物系统。那些表现出分子的有序空间排列（非中心对称）的。在这种情况下，这种系统在与强烈的激光脉冲相互作用时，自然会产生两倍于原始激光脉冲频率的光。这种SHG光用于对标本进行成像，其方式与双光子荧光显微镜中使用的荧光大致相同。然而，这种技术的利用仅限于利用产生SHG的原始光的电场矢量（偏振）的两个自由度。在这种情况下，极化是用来产生的标本的分子对称性的信息。该技术将利用光的全三维偏振状态，从而首次产生三维偏振SHG。三维偏振SHG显微镜将创建整合矢量光束与标准偏振光学。具体来说，径向偏振矢量光束在显微镜下产生增强的偏振。S聚焦，而横向偏振分量则由商用偏振光学器件操纵获得。这种新仪器将促进生物发现的进步，并为生物科学和工程专业的本科生和研究生提供独特的培训和教育机会。通过跨学科的研究和发展，这些学科的学生将深入了解设计和开发的基础知识以及细胞生物学。

A grant is awarded to Dr. Toussaint of the University of Illinois at Urbana-Champaign to develop a three-dimensional polarization second harmonic generation microscope. This approach is an alternative approach to traditional fluorescence microscopy using nonlinear optical scattering to completely obviate any reliance on exogenous probes, and rather uses the chemical properties of the specimen under study as the contrast agent, thereby allowing for truly noninvasive imaging. The caveat here is that SHG microscopy works for a special, but extremely relevant, class of biological systems?those that exhibit an ordered spatial arrangement of molecules (noncentrosymmetry). In this case, such systems upon interacting with an intense laser pulse naturally produce light at twice the frequency of the original laser pulse. This SHG light is what is used to image specimens in much the same way as fluorescence is used in two-photon fluorescence microscopy. However, utilization of this technique has been limited to exploiting only two degrees-of-freedom of the electric field vector (polarization) of the original light generating the SHG. In this case, the polarization is used to yield information on the molecular symmetries of specimens. The proposed technique will utilize the full 3D state of polarization of the light in order to generate, for the first time, three-dimensional polarization SHG. Three-dimensional polarization SHG microscopy will be created by integrating vector beams with standard polarization optics. Specifically, a radially polarized vector beam produces an enhanced polarization at a microscope?s focus, while the transverse polarization components are obtained from manipulation of commercial polarization optics. This new instrument will allow for advances in biological discovery as well as provide unique training and educational opportunities to undergraduate and graduate students in the biological sciences as well as engineering. Through interdisciplinary research and development students across these disciplines will gain insights into the fundamentals of design and development as well as cell biology.