Crosstalk reduction of silicon waveguide array by high-reflection boundary

Large-scale integrated optical phased arrays (OPAs) can provide small angular resolutions for LiDAR applications. However, strong coupling between waveguides will occur under sub-wavelength element pitch, posing a limitation to the development of high-performance OPAs. To reduce the coupling between waveguides, high-reflection boundaries made up of high-contrast gratings (HCGs) are arranged on both sides along silicon strip waveguides. At the same time, light is radiated into free space with controlled radiating rates by the HCGs periodically perturbing evanescent fields of silicon strip waveguide. Simulation results show that the crosstalk reduction of the designed array is over 10 dB compared to traditional waveguide array with identical sizes within the wavelength ranges of 1500 ~ 1590 nm. Furthermore, a weak radiation strength of 1.15 mm-1 is achieved, yielded an effective radiation length up to 2 mm. Therefore, combining with the low crosstalk between under the deigned sub-wavelength element pitch of 0.645λ and the long effective radiation length, our design holds promise for high-performance OPAs with a large field of view and a high angular resolution.