Sub-wavelength semiconductor nanowires have been attracting strong interest recently for photonic applications because they possess various unique optical properties and offer great potential for miniaturizing devices. However, with these nanowires, it is not easy to realize tight light confinement or efficient coupling with photonic circuits. Here we show that a high Q nanocavity can be created by placing a single III/V semiconductor nanowire with the diameter less than 100 nm in a grooved waveguide in a Si photonic crystal, and employing nanoprobe manipulation. We have observed very fast spontaneous emission (91 ps) from nanowires accelerated by the strong Purcell enhancement in nanocavities, which proves that unprecedented strong light confinement can be achieved in nanowires. Furthermore, this unique system enables us to move the nanocavity anywhere along the waveguide. This configuration provides us tremendous flexibility in integrated photonics because we can add and displace various functionalities of III/V nanocavity devices in Si photonic circuits.

Nanocavity lasers are commonly characterized by the spontaneous coupling coefficient β that represents the fraction of photons emitted into the lasing mode. While β is conventionally discussed in semiconductor lasers where the photon lifetime is much shorter than the carrier lifetime (class-B lasers), little is known about β in atomic lasers where the photon lifetime is much longer than the other lifetimes and only the photon degree of freedom exists (class-A lasers). We investigate the impact of the spontaneous coupling coefficient β on lasing properties in the class-A limit by extending the well-known Scully–Lamb master equation. We demonstrate that in the class-A limit all the photon statistics are uniquely characterized by β and that the laser phase transition-like analogy becomes transparent. In fact, β perfectly represents the “system size” in phase transition. Finally, we investigate the laser-phase transition analogy from the standpoint of a quantum dissipative system. Calculating a Liouvillian gap, we clarify the relation between β and the continuous phase symmetry breaking.

We demonstrate optically pumped telecom-band lasing in single InAs/InP nanowires at room temperature.

We demonstrated sub-wavelength (~111 nm diameter) single nanowire (NW) continuous wave (CW) lasers on silicon photonic crystal in the telecom-band with direct modulation at 10 Gb/s by optical pumping at cryogenic temperatures. To estimate the small signal response and pseudo-random bit sequence (PRBS) modulation of our CW lasers, we employed a new signal detection technique that employs a superconducting single photon detector and a time-correlated single photon counting module. The results showed that our NW laser was unambiguously modulated at above 10 Gb/s and an open eye pattern was obtained. This is the first demonstration of a telecom-band CW NW laser with high-speed PRBS modulation.

We report on the fabrication, nanomanipulation, and optical properties of ZnO-nanowire-induced nanocavities in grooved SiN photonic crystals. We show that subwavelength ZnO nanowires supporting intrinsically no Fabry−Peŕot mode in the violet and near-ultraviolet range can induce optical confinement when introduced in a grooved twodimensional photonic crystal waveguide. Despite fabrication challenges arising at such short wavelengths, this hybrid approach leads to fundamental nanocavity modes with resolution-limited quality factors larger than Q exp = 2.1 × 10 3 at λ = 403 nm for a mode volume V m = 5.9(λ/n r NW ) 3 = 3.4(λ/n r SiN ) 3 , as deduced from three-dimensional finite-difference timedomain calculations. The investigation of optical losses in our system shows that at wavelengths shorter than λ = 390 nm Q exp is limited by self-absorption, indicating a good nanowire to cavity coupling. These results validate our hybrid approach as an efficient way to circumvent the processing issues that were so far preventing the insertion of ZnO emitters in photonic crystal nanocavities. Furthermore, we demonstrate that the degree of freedom along the groove can be used to move nanowire-induced nanocavities in space, position them deterministically, and tune their optical properties in the near-ultraviolet range. This striking feature opens the path toward the realization of versatile nanophotonic devices including movable and tunable all-dielectric NW nanolasers operating at high temperature.