Strong Bragg gratings for WDM devices in non-sensitised low-loss Ge-doped waveguides

Bragg gratings have been written with 193 nm UV-light through a phase mask in low-loss germanium-doped buried waveguides. Without any kind of sensitisation, reflectivities of up to 99.98% and background rejection better than 22 dB have been obtained for 20 mm long Bragg gratings.