title: Robust Self-Referencing Method for Chiral Sum Frequency Generation Spectroscopy.
abstract: Chiral sum frequency generation spectroscopy (SFG) is of great interest for studying biological systems, among others. Whereas the chiral response in circular dichroism is about 0.1% of the achiral response, the chiral SFG response can be the same order of magnitude as the achiral SFG signal. However, chiral SFG is limited by the attainable signal-to-noise of the weak nonlinear signals and therefore extremely sensitive to proper alignment. We present a robust method for chiral SFG and demonstrate the use on solid-air surfaces with achiral and chiral molecules. We simultaneously measure two orthogonal polarizations-either the interference chiral SFG (±45° polarized) or the pure chiral and achiral SFG-using a waveplate and beam displacer. Both optics are placed in the detection arm and can be easily incorporated into any SFG setup. Furthermore, we employ self-referencing to calibrate alignment for each sample individually using a polarizer in the detection arm. These methods greatly increase the reliability and quality of chiral SFG measurements.
authors: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
authors: M Luke
authors: ML
authors: McDermott
authors: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
authors: Poul B
authors: PB
authors: Petersen