Planar waveguide echelle gratings: an embeddable diffractive element for photonic integrated circuits

We have demonstrated a 40-channel echelle grating demultiplexer with a 100 GHz channel spacing, using silica-on-silicon planar waveguides. Figure 3 shows the output spectrum of several channels, measured using a tunable laser source. The measured cross-talk is better than -35 dB, the insertion loss is approximately 5 dB including fibre-to-waveguide coupling, and the polarization birefringence has been eliminated using a modified compensator …