title: Optical piezoelectric transducer for nano-ultrasonics.
abstract: Piezoelectric semiconductor strained layers can be treated as piezoelectric transducers to generate nanometer-wavelength and THz-frequency acoustic waves. The mechanism of nano-acoustic wave (NAW) generation in strained piezoelectric layers, induced by femtosecond optical pulses, can be modeled by a macroscopic elastic continuum theory. The optical absorption change of the strained layers modulated by NAW through quantum-confined Franz-Keldysh (QCFK) effects allows optical detection of the propagating NAW. Based on these piezoelectric-based optical principles, we have designed an optical piezoelectric transducer (OPT) to generate NAW. The optically generated NAW is then applied to one-dimensional (1-D) ultrasonic scan for thickness measurement, which is the first step toward multidimensional nano-ultrasonic imaging. By launching a NAW pulse and resolving the returned acoustic echo signal with femtosecond optical pulses, the thickness of the studied layer can be measured with <1 nm resolution. This nano-structured OPT technique will provide the key toward the realization of nano-ultrasonics, which is analogous to the typical ultrasonic techniques but in a nanometer scale.
authors.affiliation: Graduate Institute of Electro-Optical Engineering, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Kung-Hsuan
authors.initials: KH
authors.lastname: Lin
authors.forename: Gia-Wei
authors.initials: GW
authors.lastname: Chern
authors.forename: Cheng-Ta
authors.initials: CT
authors.lastname: Yu
authors.forename: Tzu-Ming
authors.initials: TM
authors.lastname: Liu
authors.forename: Chang-Chi
authors.initials: CC
authors.lastname: Pan
authors.forename: Guan-Ting
authors.initials: GT
authors.lastname: Chen
authors.forename: Jen-Inn
authors.initials: JI
authors.lastname: Chyi
authors.forename: Sheng-Wen
authors.initials: SW
authors.lastname: Huang
authors.forename: Pai-Chi
authors.initials: PC
authors.lastname: Li
authors.forename: Chi-Kuang
authors.initials: CK
authors.lastname: Sun
mesh_terms: D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation*; D012666:Semiconductors; D014159:Transducers; D014465:Ultrasonics