High sensitivity and large scanning range optical antennas enabled by multi-casting ridge-waveguide subwavelength structure arrays

With the rapid development of large-scale integrated photonics, optical phased array (OPA) is an effective way to realize highly integrated, stable and low-cost beam control system. Achieving a large field of view (FOV) in the longitudinal direction without increasing fabrication cost and system complexity is still a significant challenge in OPA antennas. Here, a high sensitivity and large scanning range antenna based on subwavelength structure array is proposed to enhance the longitudinal scanning and free-space radiating efficiency by using the ridge-waveguide structure and backward-emitting. A millimeter-long grating antenna with a far-field beam divergence of 0.13{\deg} and a wavelength sensitivity of 0.237{\deg}/nm is experimentally demonstrated. Furthermore, by using different sideband periods, we introduce a multi-casting grating antenna with a large scanning range up to 42.6{\deg}. The proposed devices show significant improvement in longitudinal wavelength sensitivity compared with the typical waveguide grating antennas.