Periodic dielectric waveguide-based cross- and T-connections with a resonant cavity at the junctions

We propose a cross-connection and a T-connection in periodic dielectric waveguides (PDWs) with ultrasmall size and high transmission efficiency at λ = 1.55 μm. The cross-connection was formed by introducing a 3 × 3 square dielectric resonant cavity at the cross-junction with a crosstalk of less than 0.8% (about − 21 dB) and a transmission of larger than 93% at the desired output port. The T-connection was formed by introducing a 3 × 5 dielectric resonant cavity with modifications at the T-junction. The total transmission is up to 95%. In addition, different power splitting ratios were also achieved by moving the input waveguide of the T-connection with different displacements.