Vibrational Spectra of Liquid Interfaces with A 100 kHz Sub-1 cm-1 High Resolution Broadband Sum Frequency Generation Vibrational Spectrometer (HR-BB-SFG-VS)

Sub-1 cm-1 high-resolution broadband sum-frequency generation vibrational spectrometer (HR-BB-SFG-VS) using synchronized picosecond and femtosecond lasers at 1 kHz was first reported over a decade ago, and many advantages of the HR-BB-SFG-VS over the conventional BB-SFG-VS have been well-documented. A high-efficient and low-cost version of the HR-BB-SFG-VS is needed for broader adoption of this powerful interface specific spectroscopic technique. Here, we report the realization of such a sub-1 cm-1 HR-BB-SFG-VS with a tunable repetition rate around 100 kHz. Instead of synchronization of an additional expensive 90 picosecond laser for enough power to achieve high spectral resolution SFG measurement, a chirped volume Bragg grating (CVBG) is implemented with the second harmonic band compression (SHBC) unit to generate an intense 90 picosecond laser pulse at 517 nm with a bandwidth of about 0.16 cm-1 from a 150-fs laser pulse at ~1034 nm, with an efficiency of ~26%. The effectiveness of this new SFG system is demonstrated through the SFG spectra obtained with a spectral resolution of 0.6 cm-1 and excellent lineshape from the air/DMSO aqueous solutions interfaces, and the air/water interface, without apparent surface heating effect. This development provides a low-cost and easy-to-implement powerful HR-BB-SFG-VS instrumentation for broad applications in structure and dynamics studies on the illusive molecular surfaces and interfaces.