Researcher(s)
- Robin Depto, Electrical Engineering, University of Delaware
Faculty Mentor(s)
- Tingyi Gu, Electrical & Computer Engineering, University of Delaware
Abstract
When two dialectic waveguides are within proximity of each other, the evanescent tail of the electromagnetic field in each interacts with the core of the other. These interactions result in a coupling of the waveguides and an exchange of power between them. This phenomenon can be exploited to transfer light from an external waveguide into a microring resonator, or between two microring resonators. Evanescent coupling of waveguides can be analyzed using Coupled Mode Theory (CMT), which is derived from Maxwell’s equations. CMT is more sophisticated than other models that estimate waveguide loss in that it considers the statistical distribution of the roughness of the waveguides’ walls.
Ongoing work in the laboratory group involved a Mach-Zehnder parallel ring resonator network in silicon. An unexpected result had been observed: In addition to dips in the overall transmission through the network at the rings’ resonant frequency, there was a peak. That transmission depends on wavelength of input light was known, but this did not explain the observed peak.
In the present work, a simulation was created in MATLAB implementing CMT of resonators. The code was written to compute and plot overall transmission T as the dependent variable. Both wavelength λ of input light and detuning Δφ between the two parallel arms were independent variables. Simulation results showed that there is a strong interaction between the two independent variables. Depending on the value of one, a slight difference in the other will drastically affect overall transmission. With this understanding, it is clear that both parameters λ and Δφ need to be carefully controlled in order for the device to behave as intended.