Credit: © 2007 Nature

Quantum dots and photonic crystals are two of the most intensely studied systems in labs around the world, so it is no surprise that researchers are also interested in the interactions between these two types of structures. Jelena Vuc̆kovic̆ and co-workers at Stanford University and the University of California, Santa Barbara, have now shown that a single quantum dot can control the reflectivity of a cavity in a photonic crystal.

Photonic crystals are periodic structures that are transparent to light in certain wavelength ranges. The periodicity of the gallium arsenide photonic crystal studied by Vuc̆kovic̆ and co-workers was disrupted by a defect to create a cavity with a resonant mode at a wavelength of 926 nm. This cavity was coupled to an indium arsenide quantum dot, which had a characteristic emission wavelength that depended on its temperature.

The Stanford–Santa Barbara team showed that the quantum dot could change the reflectivity of the cavity by as much as 40% under certain conditions and that the system behaves as predicted by theory in both the weak and strong coupling regimes. The work could have applications in quantum information processing.