Tunable narrow band sources for anisotropic THz spectroscopy*

THz spectroscopy is well suited for material identification and characterization in many different fields due to unique molecular vibrational signatures in this range. Recently this has been extended to feature identification in large biomolecules like proteins and DNA, using the newly developed time domain Anisotropic Terahertz Microscopy (ATM)[1]. ATM measures polarization dependent changes in THz absorption and thus generates a comprehensive map of the vibrational modes, featuring their frequencies as well as their directions. Despite these advances, proliferation of THz systems is hindered by low dynamic ranges of measuring systems, large footprints and cost. Therefore, development of high power, compact THz sources and their characterization are critical. In this study we investigate the suitability of using quasi CW THz radiation generated by pumping Orientation Patterned Gallium Phosphide with a 1064 nm fiber laser for identifying anisotropic signatures of molecular crystals.THz generation from 0.5 to 4 THz is achieved. Results compared with that obtained using a broadband time domain spectrometer. The results show that new narrow band sources are suitable for high dynamic range THz systems.
1. Niessen, K.A., et al., Biophys. J., 2017