Resonator/waveguide coupling in phononic crystals for demultiplexing and filtering applications

In this paper, we report the design, fabrication, and characterization of different VHF resonators communicating through a PnC waveguide. Waveguide-based resonators are employed because of their high-Q, compactness, large spurious-free spectral ranges, and the possibility of better control over coupling to PnC waveguides. Two different mechanisms of coupling (direct and side coupling) are utilized and demonstrated. It is also shown that by modifying the defects in the formation of the resonator, the frequency of the resonance can be tuned. It is shown that the signal sent through the waveguide can be picked up by the matching resonator, while the cross coupling to the other resonators at a different frequency of resonance is at the noise level. These demonstrations evidence the possibility of realizing complex signal processing devices using coupled PnC waveguides and resonators in a low loss platform.