title: THz Acoustic Spectroscopy by using Double Quantum Wells and Ultrafast Optical Spectroscopy.
abstract: GaN is a pivotal material for acoustic transducers and acoustic spectroscopy in the THz regime, but its THz phonon properties have not been experimentally and comprehensively studied. In this report, we demonstrate how to use double quantum wells as a THz acoustic transducer for measuring generated acoustic phonons and deriving a broadband acoustic spectrum with continuous frequencies. We experimentally investigated the sub-THz frequency dependence of acoustic attenuation (i.e., phonon mean-free paths) in GaN, in addition to its physical origins such as anharmonic scattering, defect scattering, and boundary scattering. A new upper limit of attenuation caused by anharmonic scattering, which is lower than previously reported values, was obtained. Our results should be noteworthy for THz acoustic spectroscopy and for gaining a fundamental understanding of heat conduction.
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Fan Jun
authors.initials: FJ
authors.lastname: Wei
authors.affiliation: Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan.
authors.forename: Yu-Hsiang
authors.initials: YH
authors.lastname: Yeh
authors.affiliation: Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan.
authors.forename: Jinn-Kong
authors.initials: JK
authors.lastname: Sheu
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.|Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Kung-Hsuan
authors.initials: KH
authors.lastname: Lin