Letter abstract
Nature Nanotechnology 2, 704 - 708 (2007)
Published online: 14 October 2007 | doi:10.1038/nnano.2007.319
Subject Category: Photonic structures and devices
Spatial manipulation of nanoacoustic waves with nanoscale spot sizes
Kung-Hsuan Lin1,5, Chih-Ming Lai2, Chang-Chi Pan3, Jen-Inn Chyi3, Jin-Wei Shi3, Shih-Ze Sun1, Chieh-Feng Chang1 & Chi-Kuang Sun1,4
Abstract
Coherent acoustic phonons are generated at terahertz frequencies when semiconductor quantum-well nanostructures are illuminated by femtosecond laser pulses1, 2, 3, 4, 5, 6, 7, 8, 9. These phonons—also known as nanoacoustic waves—typically have wavelengths of tens of nanometres, which could prove useful in applications such as non-invasive ultrasonic imaging10, 11, 12 and sound amplification by the stimulated emission of radiation13. However, optical diffraction effects mean that the nanoacoustic waves are produced with spot sizes on the micrometre scale. Near-field optical techniques can produce waves with smaller spot sizes, but they only work near surfaces14. Here, we show that a far-field optical technique—which suffers no such restrictions—can be used to spatially manipulate the phonon generation process so that nanoacoustic waves are emitted with lateral dimensions that are much smaller than the laser wavelength. We demonstrate that nanoacoustic waves with wavelengths and spot sizes of the order of 10 nm and 100 nm, respectively, can be generated and detected.
- Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
- Department of Electronic Engineering, Ming Chuan University, Taoyuan 33348, Taiwan
- Department of Electrical Engineering, National Central University, Jhongli 32054, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
- Present address: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Correspondence to: Chi-Kuang Sun1,4 e-mail: sun@cc.ee.ntu.edu.tw
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