Efficient coupling between guided optical modes in ZnO nanowire-waveguides and tapered silica fibers

We combine top-down and bottom-up processes for the fabrication of photonic nanowires to efficiently inject and extract light from waveguide modes of ZnO nanowires lying on low refractive index silica aerogel substrates. Our approach relies on the emission of propagating modes of the light field from a tapered silica fiber and the efficient coupling of the emitted field into the high-index ZnO nanowires. We show that this approach provides a robust and surprisingly efficient technique to study the waveguiding properties of semiconductor nanowires. The experimental results are confirmed and quantified by numerical simulations of the different coupling processes using a finite difference time domain approach. We discuss potential applications of this technique for further experiments, which combine passive and active nanoscale photonic elements.