Optical properties of circular Bragg gratings in labyrinth geometry

We present an optical study of new device designs for electrically contactable circular Bragg grating cavities in labyrinth geometries. We propose to rotate the connections between adjacent rings to disable waveguiding and improve the mode confinement. 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 performed polarization resolved measurements to investigate whether the connections create asymmetries in the photonic confinement that would impede the performance of the device.