Design and optimization of polymer ring resonator modulators for analog microwave photonic applications

Efficient modulation of electrical signals onto an optical carrier remains the main challenge in full implementation of microwave photonic links (MPLs) for applications such as antenna remoting and wireless access networks. Current MPLs utilize Mach-Zehnder Interferometers (MZI) with sinusoidal transfer function as electro-optic modulators causing nonlinear distortions in the link. Recently ring resonator modulators (RRM) consisting of a ring resonator coupled to a base waveguide attracted interest to enhance linearity, reduce the size and power consumption in MPLs. Fabrication of a RRM is more challenging than the MZI not only in fabrication process but also in designing and optimization steps. Although RRM can be analyzed theoretically for MPLs, physical structures need to be designed and optimized utilizing simulation techniques in both optical and microwave regimes with consideration of specific material properties. Designing and optimization steps are conducted utilizing full-wave simulation software package and RRM function analyzed in both passive and active forms and confirmed through theoretical analysis. It is shown that RRM can be completely designed and analyzed utilizing full-wave simulation techniques and as a result linearity effect of the modulator on MPLs can be studied and optimized. The material nonlinearity response can be determined computationally and included in modulator design and readily adaptable for analyzing other materials such as silicon or structures where theoretical analysis is not easily achieved.