The Development of Four-Wave Mixing Spectroscopy to Measure Vibrational Spectra in the Low-Frequency Terahertz Range*

We report the progress of developing four-wave mixing spectroscopy to measure vibrational spectra in the low-frequency terahertz range. The optical tabletop system, we have improved in the Laser Spectroscopy Lab at the University of West Florida is a multipurpose system [1], capable of executing a variety of spectroscopy methods such as e.g. Raman, Coherent Raman, and Laser-Induced Breakdown spectroscopy. For this project, our focus is on Coherent Raman Spectroscopy, through three-color two-beam broadband nonlinear frequency mixing. The three-color nature of the four-wave mixing signal allows for an effective non-resonant signal suppression relative to the polarized and depolarized Raman bands. This type of nonlinear four-wave mixing has not been fully utilized for ultrafast coherent Raman microscopy. To demonstrate the precision and merit of our modified system, we present measured and processed spectra of liquid and crystalline samples and provide a characterization of the critical components that constitute our system.

[1] Laszlo Ujj, “Contribution to the development of low-frequency terahertz coherent Raman micro-spectroscopy and microscopy “, Research article, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2018, Volume 199, 15, Pages 448-454.