Optical piezoelectric transducer for nano-ultrasonics.
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.
Lin
Kung-Hsuan
KH
Graduate Institute of Electro-Optical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Chern
Gia-Wei
GW
Yu
Cheng-Ta
CT
Liu
Tzu-Ming
TM
Pan
Chang-Chi
CC
Chen
Guan-Ting
GT
Chyi
Jen-Inn
JI
Huang
Sheng-Wen
SW
Li
Pai-Chi
PC
Sun
Chi-Kuang
CK
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