MRI:ID - Development of an Imaging Nonlinear Optical Ellipsometer

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With this award from the Major Research Instrumentation program (MRI), Garth Simpson and colleagues of Purdue University will develop a SHG microscope with full polarization capability to enhance nonlinear optical Stokes ellipsometry (NOSE). The instrument will consist of an inverted optical microscope modified to allow confocal imaging in a beam-scanning configuration. The microscope will be equipped with a photoelastic modulator for rapid polarization modulation, a pair of photomultiplier tubes (PMTs) for polarization-dependent SHG detection, and a pair of PMTs for polarization dependent two photon excited fluorescence (TPEF) detection. This instrument will yield detailed polarization information and nanoscale structural information, obtained from molecular tensors and theoretical modeling. This instrument will be utilized initially to study cell wall construction (through cytoskeletal actin-myosin network dynamics) and deconstruction (enzymatic degradation of cellulosic materials for renewable energy) mechanisms. These efforts will capitalize on the chiral-specific activities of second harmonic generation (SHG), which allow for determination of absolute polar orientation and the degree of coparallel versus anti-parallel alignment within fibrous assemblies. This instrument will affect a broad range of research areas involving surfaces and interfaces.