Junction-less optical phase shifter loaded silicon Mach-Zehnder modulator

In this paper, we design and numerically analyze the performance of electrostatic doping (ED) assisted junction-less optical phase shifter loaded silicon Mach-Zehnder (MZM), which is realizable on the 220 nm SOI platform. The proposed phase shifter contains a vertical metal-insulator-semiconductor (MIS) junction and a lateral metal-semiconductor (MS) junction. Change in the refractive index profile inside the rib waveguide, which supports the phase shifter is achieved by altering the concentration of free carriers via the plasma dispersion effect. Numerical simulation using a commercially available TCAD tool and mode solver are used to estimate the performance of the proposed modulator. Two different sets of materials are used as electrodes to realize the MIS-MS charge plasma diode. In one design, gold (Au) and silver (Ag) is used as the electrode materials, while the other design utilizes palladium (Pd) and aluminum (Al) as the electrode materials. The performance of the proposed modulator(s) is extensively studied both in the steady state and transient state. A complete analysis of the chirp and nonlinear distortion for the proposed modulator are also presented in the paper. Results predict that a maximum of 15.4 dB dynamic extinction ratio (ER) is achievable with a minimum of 3.2 dB insertion loss (IL). The proposed modulator is expected to provide a maximum of 30.3 Gbps operating speed with 22.2 GHz of 3-dB electro-optical bandwidth. Simulation result predicts that the worst case dynamic energy per bit for the proposed ED assisted MZM is approximately 54.4 fJ/bit.