Polarization Sensitive Low Frequency Raman and Coherent Raman Spectrum of Crystals*

     We have measured the polarization-sensitive vibrational phonon spectra of a single crystal of cubic symmetry, Bismuth Germanate with the chemical formula Bi₃Ge₄O₁₂ (BGO). We observed the phonon modes connected to the symmetry species of the crystal. First, the polarization sensitive Raman spectra were measured at specific configurations allowing us to distinguish and associate band frequencies to the A, E and F modes in accordance with group theory. We used and modified the laser system available at the laser spectroscopy lab at the University of West Florida to obtain the proper polarizations and excitation conditions necessary to isolate the modes.

    Second, we have designed the polarization conditions for the actinic laser beams to measure the two beam 3-color broadband coherent Raman spectra (3CBCRS [1,2]) of BGO. The background free spectra were consistent with the spontaneous Raman spectra. This poster presents one of these measured and processed spectra of the low-frequency phonon modes. The background-free spectra were consistent with the spontaneous Raman spectra. It is proved here that the coherent Raman measurements can be used to identify the symmetry species associated with the different phonon modes as well as in the former method.

1. L. Ujj, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 199 (2018) 448–454.

2. L. Ujj, T. Olsson, B. Schundelmier, T. Bestor, Vib Spectrosc. 108 (2020) 103056.