Design Considerations of Silicon Nitride Optical Phased Array for Visible Light Communications

Design considerations and guidelines for utilizing an array of silicon nitride grating couplers for point-to-point communication with the ability of two-dimensional (2-D) beam steering are investigated using numerical simulations. A single grating coupler is designed to enable efficient and directional radiation. The spacing of couplers in the array is optimized in order to decrease the level of the cross-talk (< -65 dB) as well as reducing the number of unwanted side lobes. The number of elements in an array is examined for both 1-D and 2-D designs in order to achieve efficient radiation. Moreover, a phased array of 50 elements, with an aperture area of 40 mu m x 75 mu m, is proposed taking into account the tradeoff between the footprint and radiation efficiency. The radiation pattern of the designed array is investigated with full-wave simulation and compared to theoretical expectations. Beam steering in azimuth angle, using thermo-optical phase shifters is studied. Beam steering in polar angle is studied by exploiting wavelength tuning. The loss of the free space link regarding the designed array in different distances is obtained to study the range of the optical wireless communication link.