**4. Conclusions**

The full-vectorial finite-difference method was used to calculate the single-mode conditions, mode sizes, and optical power distribution of the PE channel waveguides. The widths of the PE waveguides were optimized to 1.2 μm. The propagation losses of the guided mode at different separation distances between the electrodes were analyzed and discussed. As a very important aspect of the practical application, the half-wave voltages were simulated using FD-BPM. The thickness of the PE waveguides and the separation distances between the electrodes were optimized to 0.15 μm and 8.08 μm, respectively. The optimized value of Vπ·L was calculated to be 10.2 V·cm.

**Author Contributions:** B.X. conceived the original idea; H.H. carried out the simulations and wrote the manuscript; H.H., B.X., T.L., G.C. and S.R. contributed the useful and deep discussions, analyzed the data and modified the manuscript.

**Funding:** This work was supported by the Shenzhen Science and Technology Planning (NO. JCYJ20170818143327496), the Project of Youth Innovative Talents in Higher Education Institutions of Guangdong (NO. 2018KQNCX399), the Foundation of Zibo Vocational Institute (NO. 2018zzzr03), the School City Integration Development Plan of Zibo (NO. 2019ZBXC127), and the Shandong University Science and Technology Planning (NO. J16LN93).

**Conflicts of Interest:** The authors declare no conflict of interest.
