Self-consistent physics-based and electromagnetic model travelling-wave semiconductor RF photonic devices

Distributed structures exploited for high-speed semiconductor RF photonic devices, such as electro-optic, electro-absorption modulators (EOMs and EAMs), and photodetectors (PDs), exhibit a complex interplay between the optical waveguide and the RF structure, usually located by a pn, pin, or Schottky junction in reverse bias. In such devices (with micron or sub-micron cross section) the RF signal propagation is affected by strong low-frequency dispersion due to metal and semiconductor losses. An even more significant effect is played by slow-wave propagation, caused by magnetic field penetration into the semiconductor layers wherein the electrical field is screened, with obvious implications for the optical-RF phase velocity mismatch. Finally, the RF propagation characteristics strongly depend on the DC working point (electrical and/or optical), thus suggesting that large signal performance evaluation requires a non-linear distributed model. In the present paper, we propose a novel quasi-static finite element model for the RF propagation in distributed semiconductor structures.