Abstract
A Raman inactive LO3 phonon mode of Strontium Titanate (SrTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) has been successfully excited through mode-selective phonon excitation (MSPE) method using a mid-infrared free electron laser (MIR-FEL) at Kyoto University. Hyper-Raman scattering (HRS) spectroscopy was employed to observe and confirm the selective excitation of this target Raman forbidden mode. As preliminary experiments, anti-Stokes HRS of LO3 phonon mode was carried out without FEL irradiation at room temperature and at 5 K. Additionally, by observing the sum frequency generation (SFG) from ZnS Cleartran <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> , the synchronization of the MIR-FEL and ps-laser pulses was achieved. Finally, selective excitation of the target LO3 phonon mode was demonstrated through anti-Stokes HRS spectroscopy at 5 K. A red shifted phenomenon was recognized since the selectively excited LO3 phonon appeared at 770 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> instead of around 800 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> .
Published Version
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