Design and Simulation of Dual Polarization GST-on-Silicon Nitride Optical Modulator

Application of Silicon-based optical modulators in some wavelength ranges (such as O-band) is challenging because of the two photon absorption (TPA) effect of Si. Silicon nitride (Si3N4), on the other hand has a larger bandgap compared to Si, which minimizes the TPA effect in it. The lack of fast free carrier dispersion effects and relatively large footprint of Si3N4optical waveguides are the basic shortcomings of Si3N4-based devices. Here, integration of the phase change material of Ge2Sb2Te5within the Si3N4waveguides is proposed as a solution to overcome both these limitations. Phase transition of the GST provides a mechanism for optical modulation while large variation in its refractive index during the phase transitions, reduces the length of the modulators. A dual polarization optical modulator is designed in this manuscript, which according to our simulations provides respectively, the reasonable insertion loss and high extinction ratio of ~1.15dB, and 8.12dB for the TE, and low insertion loss of ~0.57dB, and the extinction of 1.75dB, for the TM polarized light. Furthermore, the proposed structure offers ultra-wide optical bandwidth of 500nm (covering O-band to U-band), small overall footprint 2.4µm2, and its bitrate and energy consumption is estimated to be about 0.4Gbit/sec and 12pJ, respectively.