Harnessing light with photonic nanowires: fundamentals and applications to quantum optics

The efficient feeding of spontaneous emission (SE) into a controlled optical mode lies at the heart of a new generation of advanced optoelectronic devices, such as low-threshold microlasers and bright sources of quantum light. In the solid state, single-mode emission was first demonstrated by using the Purcell effect that arises in a resonant microcavity. Recently, the need to relax the constraints inherent to such a narrow-band approach has motivated large effort to develop structures ensuring broadband and efficient SE control. This minireview deals with fiber-like photonic nanowires, a class of high-index waveguides that features key assets in this context. Combining theoretical predictions and experimental results, the paper details the SE dynamics in such tiny wires. In addition, it shows how the far-field emission of a single wire can be tailored through proper engineering of the two wire ends. As an application in the field of quantum optics, we review the realization of an ultrabright single-photon source. This first device was based on a self-assembled quantum dot embedded in a wire antenna realized with a top-down fabrication process. Considering recent advances in the direct growth of tapered photonic wires, we also propose a bottom-up fabrication route to realize a complete device. In particular, this proposal ensures the optimal 3D positioning of a single emitter inside the antenna. Finally, future research and application prospects are also reviewed.