Optimizations of thermo-optic phase shifter heaters using doped silicon heaters in Rib waveguide structure

Thermo-optic phase shifter (TOPS) based on doped silicon (Si) heaters is commonly used to compensate for device structure imbalance of high-speed Mach-Zehnder modulator (MZM) due to fabrication errors. However, this functionality required more electrical power for setting the MZM to be active around the linear transfer function at π/2 phase shift. To solve this issue, we proposed an optimal design of doped Si heaters using the standard commercial 220 nm Si layer in rib waveguide structure which can improve the electrical energy efficiency and reduce optical losses. Numerical simulations and optimizations were carried out on the key parameters, heater locations, doping concentration, etching depth, and laser wavelength drift. Results show that the optimal design has a low power consumption of 19.1 mW for obtaining a phase shift of π with a good time constant of 2.47 µs and low optical losses of 2.37 dB/cm at the 1550 nm operated wavelength. Thus, an excellent figure of merit (FOM) of 47.2 mWµs is obtained for the optimal design. Also, the proposed device has good stability to the laser wavelength drift effect in the C-band range. This TOPS can be very useful for improving the transmitter system performances based on high-speed MZM technology.