Spatial manipulation of nanoacoustic waves with nanoscale spot sizes

Kung Hsuan Lin, Chih Ming Lai, Chang Chi Pan, Jen Inn Chyi, Jin Wei Shi, Shih Ze Sun, Chieh Feng Chang, Chi Kuang Sun

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Coherent acoustic phonons are generated at terahertz frequencies when semiconductor quantum-well nanostructures are illuminated by femtosecond laser pulses. 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 imaging and sound amplification by the stimulated emission of radiation. 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 surfaces. Here, we show that a far-field optical techniqu - which suffers no such restriction - 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.

Original languageEnglish
Pages (from-to)704-708
Number of pages5
JournalNature Nanotechnology
Issue number11
StatePublished - Nov 2007


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