Omni-directional active pillar arrays for emission extraction and on-chip generation of optical vortices at 1.55$\mu$m

We engineer deterministic aperiodic structures (DAS) for omni-directional light extraction, emission profile shaping and direct orbital angular momentum generation from Si-based light emitting devices operating at telecom wavelengths. Omni-directional diffraction is achieved through the use of structures with circularly symmetric Fourier space and is well suited for extracting light from devices, such as LEDs or lasers. To exploit the unique light scattering properties of these structures we have fabricated active pillar arrays of Erbium (Er) doped Silicon-Rich Nitride (SRN) using electron beam lithography (EBL) and reactive ion etching (RIE) while varying geometry to optimize extraction enhancement around 1.55$\mu$m. We find that aperiodic spiral arrays with continuous circular Fourier space give over 10 times extraction enhancement and outperform Archimedean lattices, which are the standard structures commonly utilized for omni-directional extraction. Additionally we directly image the real and reciprocal space of the emitted radiation at 1.55$\mu$m and demonstrate direct generation of optical vortices with well-defined values of orbital momentum. These results offer the opportunity to engineer novel optical devices that leverage the control of structured light on optical chips, such as novel laser sources, broadband optical couplers and concentrators.