Optical properties of circular Bragg gratings with labyrinth geometry to enable electrical contacts

Abstract: We present an optical study of various device designs for electrically contactable circular Bragg grating cavities in labyrinth geometries. To create an electrical connection between the central disk and the surrounding membrane, which are separated through air gaps, we introduce connections between the adjacent rings. We propose to rotate these connections, creating a labyrinth like structure, to disable waveguiding and keep the mode confinement. To investigate how different arrangement and size of the connections affect the optical properties and to find the optimal design, six different layouts with either 3-fold or 4-fold symmetry and one with 2-fold symmetry are investigated experimentally and by numerical simulations. Reflectivity measurements and simulations show that rotating the connections improves the mode confinement, far-field pattern and Purcell factor compared to layouts with connections arranged in straight lines. We compare results between different layouts for different connection widths and perform polarization resolved measurements to investigate whether the connections create asymmetries in the photonic confinement that would impede the performance of the device.