Nanomanipulating and Tuning Ultraviolet ZnO-Nanowire-Induced Photonic Crystal Nanocavities

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–Pérot mode in the violet and near-ultraviolet range can induce optical confinement when introduced in a grooved two-dimensional 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 × 10³ 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 time-domain 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.