Two-layer optical phased array with effective subwavelength pitch for grating-lobe-free beam steering

We present a compact two-layer optical phased array (OPA) architecture implemented on a Si/SiO₂ platform that achieves an effective subwavelength pitch while maintaining sufficient physical spacing to suppress inter-waveguide crosstalk. In this design, vertical staggering of waveguides mitigates optical coupling between adjacent emitters, while the reduced effective pitch enables grating-lobe-free beam steering over a wide angular range. Finite-difference eigenmode (FDE) simulations demonstrate negligible coupling between adjacent waveguides, and full-wave finite-difference time-domain (FDTD) simulations confirm sidelobe suppression below -17 dB with a steering range approaching 100°, achieved through wavelength tuning across an 80 nm bandwidth. The proposed approach provides a scalable route to wide-angle, low-sidelobe beam steering for LiDAR, free-space optical communication, and advanced imaging systems.