Deterministic Yet Flexible Directional Light Emission from Spiral Nanomembrane Cavities

Controlling the flow of light emitted from structures in micro/nanoscale is crucial for on-chip active photonic devices and their tremendous applications. Although previous reports focus on improving the directionality along a fixed angle, the realization of flexible directional emission becomes highly desired for simultaneously manipulating multiple light flows with different properties (e.g., wavelength, polarization, and wavevector), which paves the way to emerging two and one-half dimensional and three-dimensional (3D) integrated photonics technologies. Here, we propose self-rolled-up nanomembrane-based asymmetric cavities with a deliberately controlled spiral shape and demonstrate 3D directional light emissions. The interaction between 3D confined optical resonances and a spiral nanomembrane edge results in deterministic yet tunable emission directions. Polarization-selective directionality as well as the transition between bi- and unidirectional emission regimes is revealed by adjusting the cavity c...