Wedge-Based Design for Phase Stable and Phase Accurate Heterodyne-Detected Sum-Frequency Generation Spectroscopy

Phase sensitive and heterodyne-detected (HD) sum-frequency generation (SFG) spectroscopy offers the ability to separate the nonlinear susceptibility into its real and imaginary components. This provides information about the absolute orientation of molecules at interfaces while also producing an absorptive spectrum that is linear in spectral composition and can easily be decomposed into different spectral components. However, simultaneously obtaining phase accuracy and phase stability remains a challenge in SFG. Here we present a new experimental design for HD-SFG spectroscopy that incorporates a wedge pair to accurately control the timing between the local oscillator and the sample signal. This experimental approach provides high phase accuracy and long-time phase stability in a compact and flexible configuration.

Automated summary

Phase sensitive and heterodyne-detected sum-frequency generation spectroscopy provides the ability to separate the nonlinear susceptibility into real and imaginary components. It also offers information about the absolute orientation of molecules at interfaces and produces a linear absorptive spectrum that can be easily decomposed into different spectral components. However, maintaining both phase accuracy and phase stability is still a challenge. In this study, a new experimental design incorporating a wedge pair is introduced to accurately control the timing between the local oscillator and the sample signal, resulting in high phase accuracy and long-term stability in a compact and flexible configuration.