Advanced Integrated Photonic Filters Designed with Coupled Sagnac Loop
Reflectors
Abstract
We theoretically investigate integrated photonic resonators formed by
two mutually coupled Sagnac loop reflectors (MC-SLRs). Mode interference
in the MC-SLR resonators is tailored to achieve versatile filter shapes
with high performance, which enable flexible spectral engineering for
diverse applications. By adjusting the reflectivity of the Sagnac loop
reflectors (SLRs) as well as the coupling strength between different
SLRs, we achieve optical analogues of Fano resonance with ultrahigh
spectral slope rates, wavelength interleaving / non-blocking switching
functions with significantly enhanced filtering flatness, and compact
bandpass filters with improved roll-off. In our designs the requirements
for practical applications are considered, together with detailed
analyses of the impact of structural parameters and fabrication
tolerances. These results highlight the strong potential of MC-SLR
resonators as advanced multi-functional integrated photonic filters for
flexible spectral engineering in optical communications systems.