Power-Efficient Silicon Photonic Thermo-Optic Switch Covering OESCLU-Bands Enabled by Mode-Looped Phase Shifters With Subwavelength Gratings

Ultra-broadband wavelength division multiplexing (WDM) optical networks with densely populated nodes are emerging as a principal direction for enhancing future capacity and advancing network evolution. To address this growing demand, we have developed a colorless, power-efficient thermo-optic Mach-Zehnder switch (MZS) utilizing mode-looped phase shifters. This phase shifter doubles the tuning efficiency by recirculating light through the heated region twice. The phase shifter is optimized to ensure a balanced performance across all optical communication bands, including O-, E-, S-, C-, L-, and U-bands. Furthermore, we have incorporated subwavelength grating structures (SWGs) into the adiabatic 3-dB couplers and dual-mode (de)multiplexers, which are critical for enhancing the ultra-broadband capabilities of the MZS. Experimental results demonstrate that our device achieves a switching power of 11.15 mW, with extinction ratios (ERs) surpassing 8.44 dB over a 405-nm wavelength range, and exceeding 10 dB from 1295 nm to 1675 nm. These capabilities establish our switch as a key component for future multi-band and power-efficient reconfigurable add-drop optical networks (ROADMs), with the potential to advance the telecommunications industry by supporting expanded bandwidths and enhanced efficiency.