  Subwavelength semiconductor nanowires have recently attracted interest for
photonic applications because they possess various unique optical properties
and offer great potential for miniaturizing devices. However, realizing tight
light confinement or efficient coupling with photonic circuits is not
straightforward and remains a challenge. Here we show that a high Q nanocavity
can be created by placing a single III/V semiconductor nanowire with a diameter
of under 100 nm in a grooved waveguide in a Si photonic crystal, by means of
nanoprobe manipulation. We observe very fast spontaneous emission (91 ps) from
nanowires accelerated by the strong Purcell enhancement in nanocavities, which
proves that very strong light confinement can be achieved. Furthermore, this
system enables us to move the nanocavity anywhere along the waveguide. This
configuration provides a significant degree of flexibility in integrated
photonics and permits the addition and displacement of various functionalities
of III/V nanocavity devices in Si photonic circuits.
