Thermo Optical Phase Shifter With Low Thermal Crosstalk for SOI Strip Waveguide

The trade-offs of using thermo-optical phase shifter in different standard CMOS silicon-on-insulator (SOI) structures (strip and rib waveguides) are studied. Twelve different thermo-optic phase shifters, considering metal and highly doped silicon (both n- and p-type), are studied using numerical simulations and measurements. The performance of heater type, size, and distance to the strip waveguide in terms of energy efficiency, crosstalk, and response time is investigated. The required power to reach π phase shift is measured and compared with the numerical simulation. The time response and the corresponding figure of merit of the interferometer affected by each heater is analyzed and the design strategies for optimizing the designs are discussed. A new compact design for the phase shifter is suggested with low thermal crosstalk (ΔT < 0.1 °C at a distance of 10 μm) and low electrical power consumption (Pπ = 13.2 mW).