High-Order Modes Assisted Ultra-Long Silicon Multimode Waveguide Grating Antennas

Waveguide grating antennas (WGAs) are key transmitting components for integrated optical phased arrays (OPAs). However, the typical WGAs in 220 nm silicon-on-insulator (SOI) platform suffer from high perturbation loss for TE₀ mode. In this letter, we experimentally demonstrated two ultra-long silicon multimode WGAs by TE₁ and TM₁ modes. We also fabricated two high-performance mode (de)multiplexers for generating TE₁ and TM₁ modes input. The optimized TE₁-WGA and TM₁-WGA losses are 3.58 dB/mm and 1.10 dB/mm at 1550 nm wavelength, while the measured losses are as low as 3.22 dB/mm and 1.59 dB/mm. The corresponding beam divergences with 3 mm antenna lengths are 0.0286° and 0.0267° at 1550 nm wavelength, respectively. To the best of our knowledge, this is the first demonstration of high-order mode multiplexed WGAs.