[10a-W371-1~12] 22.1 Joint Session M "Phonon Engineering"

[10a-W371-3] Selective phonon-mode excitation in diamond by mid-infrared free-electron laser

〇Oji Sato¹, Kyohei Yoshida², Heishun Zen¹, Kan Hachiya¹, Takuya Goto³, Takashi Sagawa¹, Hideaki Ohgaki¹ (1.Kyoto Univ., 2.Kumamoto Inst., 3.Doshisha Univ.)

Keywords:phonons, two-photon excitation, diamond

A Raman-active phonon mode in single-crystal diamond, which is related to superconductivity, was excited by a mid-infrared free-electron laser. As the target phonon mode (T_2g at 1,332 cm^-1) is inactive to one-photon excitation, we used two-photon excitation through MIR-FEL light irradiation which was tuned to half of the target phonon energy. Anti-Stokes Raman scattering was used to observe the excited phonon mode at cryogenic temperature where thermally excited phonons were suppressed. The anti-Stokes Raman peak was observed at around 1,300 cm^-1 only when the MIR-FEL was irradiated. Moreover, when we measured the dependence of the peak intensity on pump-laser energy, it showed second order nonlinear optical response, which suggests the two-photon excitation.