One- and two-dimensional cavity modes in ZnO microwires

We demonstrate that one-dimensional (1D) Fabry-Perot modes (FPM) and 2D whispering gallery modes (WGM) occur separately or simultaneously within a single, tapered ZnO microwire. Their observation is strongly correlated with the size and shape of the microwire cross-section. FPM can preferentially be observed in thick wires with an elongated wire cross-section without hexagonal symmetry. The formation of WGM otherwise requires hexagonal symmetry-they can be observed in thin wires having a regular hexagonal cross-section. All optical eigenmodes were unambiguously identified by their in-and out-of-(cross-sectional) plane photonic mode dispersion.