High finesse wavelength selective coupler based on ARROWs

We describe the design of an add/drop filter for wavelength division multiplexing applications that has a periodic Fabry-Perot functionality with a finesse of 100. The filter is based on a directional coupler comprising antiresonant reflecting waveguides (ARROWs) that are deliberately designed to be slightly asymmetric in order to increase the finesse. The insertion loss due to filtering is 3 dB for the selected (added/dropped) wavelengths, while the cross-talk of unselected ones is -25 dB.