Optical filter with very large stopband (≈300 nm) based on a photonic crystal vertical directional coupler

We have designed, fabricated, and demonstrated a vertical directional coupler based on the coupling between a polymer waveguide and a Wl photonic crystal waveguide. The filters have a bandwidth of ∼2 nm within a stopband of Δλ ≈ 300 nm and an on-chip insertion loss of 1 dB. This is the first (to our knowledge) demonstration of a filter with such a large stopband that overcomes the bandwidth limitation of existing filters. © 2009 Optical Society of America.