%0 PDF %T Nonlinear Interferometer: Design, implementation and phase-sensitive sum frequency generation measurement %A Wang, Jing. %D 2017-11-08T13:51:24.415-05:00 %8 2017-11-08 %R http://localhost/files/8910k5662 %X Abstract: Sum frequency generation (SFG) spectroscopy is a unique tool for probing the vibrational structure of numerous interfaces. Since SFG is a nonlinear spectroscopy, it has long been recognized that measuring only the intensity - the absolute square of the surface response - limits the potential of SFG for examining interfacial interactions and dynamics. The potential is unlocked by measuring the phase-sensitive or imaginary response. As with any phase, the phase-sensitive SFG response is measured relative to a reference; the spatial relationship between the phase reference and the sample modulates the observed interference intensity and impacts sensitivity and accuracy. We have designed and implemented a nonlinear interferometer to directly measure the phase-sensitive response. If the phase of the reference is known, then the interferometer produces an absolute phase of the surface. Compared to current configurations, phase accuracy and stability are greatly improved due to active stabilization of the sample-reference position. The design is versatile thus, can be used for any system that can be probed with SFG including buried interfaces and those with high vapor pressure. Feasibility and advantages of the interferometer are demonstrated using an octadecyltrichlorosilane (OTS) film on fused silica. Chapter 1 describes the theory of scalar sum frequency generation (SFG) spectroscopy and fundamental work on ammonia water, trimethylamine (TriMA) water and tetramethylammonium hydroxide (TMAH) water using scalar SFG. Analyzing and understanding these spectra requires phase-sensitive spectra; data left for a future student using the nonlinear interferometer. Indeed, understanding the impact of ammonia and amines on the aqueous surface was a prime motivator for developing the nonlinear interferometer. Chapter 2 is the heart of the thesis: the building, and implementation of the nonlinear interferometer. Octadecyltrichlorosilane (OTS) on silica window is used as a demonstration surface to test the validity of the nonlinear interferometer. Aqueous amines are just the starting point for applications using this nonlinear interferometer to understand chemical systems at interfaces. Detailed step-by-step alignment procedure of the nonlinear interferometer, data processing procedures, Z-scan of the non-resonance, sample preparation, dual channel approach, scalar SFG of z-cut quartz, and other phase measurement can be found in the Appendix.; Thesis (Ph.D.)--Tufts University, 2017.; Submitted to the Dept. of Chemistry.; Advisor: Mary Shultz.; Committee: Charles Sykes, Arthur Utz, and Michelle Foster.; Keyword: Physical chemistry. %[ 2022-10-11 %9 Text %~ Tufts Digital Library %W Institution