Based on the references [2,3], sol-gel materials consist of a precursor and an index modifier. Therefore, the material model of the sol-gel can be treated as its precursor with a small index change, similar to the way that doped silica for optical fiber would be. The benefit of this approach is that same material dispersion property, which is essential for some applications such as traveling wave modulation, can be used for both the precursor and the modified materials.
For this example, unfortunately, there is no material dispersion data reported in  or readily found in literature. We will use the data reported in ; the refractive indices at 1550nm are 1.500, 1.487, 1.643, and 1.328 for sol-gel core, sol-gel cladding, polymer, and top buffer layer.
In addition, the electrical properties of the material, namely the dielectric constant, is also essential to model the electric behavior of the E-O device. The dielectric constant of the sol-gel core and cladding is 3.0, based on reference . The dielectric constant of buffer material CYTOP is ~2.0 based on the datasheet from Bellex . The polymer used in ref  is AJLS102 polycarbonate, and its dielectric constant is ~2.9 .
This modulator is based on the E-O effect, hence the E-O coefficient of the polymer has to be known. Based on , the E-O coefficients are R33=170pm/V and R13= R33/3. Please note that the “crystal” orientation of the polymer (x’,y’,z’) corresponds to RSoft coordinates (x,z,y), therefore, the E-O coefficients defined in RSoft Material Editor are Rx=Rz=0, and Ry= R13 or R33 for TE or TM polarizations, as shown in Figure 2.