Nature Photon. http://dx.doi.org/10.1038/nphoton.2011.208 (2011)

The novel optical properties of quantum dots are exploited in many different applications, as are those of photonic crystals, so it is not surprising that researchers are trying to develop new classes of devices that combine quantum dots and photonic crystals. Both systems have characteristic wavelengths that depend on their composition and size or structure, and varying these wavelengths with respect to each other is a central challenge in the development of new devices. Now Hubert Krenner, of the University of Augsburg, and co-workers have demonstrated that surface acoustic waves can be used to modulate the resonant wavelength of a photonic crystal nanocavity an order of magnitude faster than before.

Krenner and colleagues — who are based in Germany, the Netherlands and the United States — directed the surface acoustic waves at the nanocavity, which contained indium arsenide quantum dots, and measured how the waves influenced the light emitted by the dots. In addition to modulation frequencies above 1.7 GHz, they demonstrated large wavelength shifts and showed that the quality factor of the nanocavity remained high and that the spatial mode profile did not change. The approach relies on the acoustic waves first stretching the nanocavity and then compressing it, which causes the resonant wavelength to first increase and then decrease.