Direction- and polarization-tunable spontaneous emission beneficial from diffraction orders of a square R6G-nanopore array.

To meet the miniaturization and compatibility of current micro-nano optical devices, two-dimensional (2D) photonic crystals (PCs), which can manipulate the optical parameters and their propagation with more degree of freedom, have become more important in nano optics. In the case of 2D PCs, the specific symmetry of the microscopic lattice arrangement determines its macroscopic optical properties. In addition, beyond this key element of lattice arrangement, the unit cell of PCs is also a critical factor in modulating the far-field optical behaviors. This work explores the manipulation of spontaneous emission (SE) of rhodamine 6G (R6G) in a square lattice of anodic aluminum oxide (AAO) membrane. The directional and polarized emissions are observed to be related to the diffraction orders (DOs) of the lattice arrangement. By further tuning the size of unit cells, different DOs are triggered to overlap with the emission of R6G, resulting in an extended tuning for directions and polarizations of light emission. It exhibits the significance for the design and application of nano optics devices.