Nature Mater. 13, 279–285 (2014)

Subwavelength optical cavities that tightly confine light offer very useful functionality for integrated photonic circuits, but it is challenging to produce them in a manner that allows them to be easily relocated. Now, Muhammad Birowosuto and colleagues from NTT Corporation in Japan have come up with an elegant solution. They placed a single III–V semiconductor (InAsP/InP) nanowire with a diameter of less than 100 nm in a square-grooved waveguide in a two-dimensional silicon photonic crystal. Thanks to the perturbation of the photonic crystal, a high-Q cavity is created around the nanowire. This cavity can be repositioned by simply moving the nanowire along the grooved waveguide using an atomic force microscope. When the cavity was excited, fast (91 ps) spontaneous emission was observed from the nanowires as a result of the Purcell effect, which is associated with the cavity. A sharp resonance associated with the cavity was observed to move in tandem with the displacement of the nanowire, confirming the effectiveness of the approach. The realization of a moveable cavity may be useful for realizing spatially tunable nanolasers and all-optical memories.

Credit: © 2014 NPG