Induced transparency in ring resonator devices

Abstract

A microring resonator consists of a ring side-coupled to a bus waveguide, where the light exchange is achieved by means of evanescent coupling mechanism.It is a strong candidate for integrated optics due to its advantage of compact size, cascadable input/output ports, and the compatibility of CMOS fabrication.The microring resonator can be used to create many interesting phenomena that are difficult to obtain in other classical configurations.This thesis focuses on the theoretical analysis and experimental realization of induced transparency in optical devices derived from ring resonators.In this thesis, I propose a ring-bus-ring Mach-Zehnder interferometer (RBRMZI) system based on a 3×3 coupler, and show that such a system can generate an electromagnetically induced transparency (EIT)-like spectrum via phase engineering facilitated by interpathways interference between RBR and MZI, instead of separate light interaction in two resonators alone.Both the transfer matrix formalism and the temporal coupled mode theory are investigated to model this induced transparency.The relationship between the two theories is obtained via the energy-conservation and Q-factors.In addition, the EIT-like spectrum in the RBRMZI is experimentally realized using silicon-oninsulator technology.The best RBRMZI device has a transparency with a bandwidth of 0.25nm, a free spectral range of 12nm and a Q-factor of ~6300.With further measurements of the devices having strong ring-bus coupling, we obtain a Q~18000 when the circumference of one ring is 43.4μm and the circumference of the other ring is slightly detuned by ~0.035%.Moreover, we achieve a roundtrip loss as small as ~0.5% of the input energy.The measurement results agree well with theoretical prediction and 2D-FDTD numerical calculations.