I believe, you just need to import voltage-dependent refractive index (real and imaginary coefficient both) in the interconnect. For this, first, you will need to run the Charge simulator followed by Mode/FDTD tools. Depending upon the opted length and structure (like MZI or MRR) you will get your result.

I agree with Sourabh Jain.

Yes. In case it's a travelling wave MZM, you need to have a travelling wave electrode (TWE) along with the phase shifter (optical modulator element) part. In the TWE, you have to provide RF loss and characteristic impedance. You can obtain these values from Mode/FDTD modules for your design.@Ebrahi Darabi

Use ion implantation scheme for doping