Application of photosensitivity in planar silica-on-silicon optical waveguides

Planar lightwave circuit (PLC) devices such as splitters, Mach-Zehnder interferometers and arrayed-waveguide grating (AWG) multiplexers, have been developed using GeO2-SiO2 waveguides on Si substrates. Such devices typically have low propagation and fiber-connection losses. Advanced optical communication systems, such as wavelength division multiplexing (WDM) systems, optical switching systems, and optical access networks[1] uses PLC devices. These silica-based planar waveguides are photosensitive[2]. This property can be used to make new types of PLC devices. For instance, photo-induced refractive index changes have been used for trimming the spectral response in the PLCs and forming Bragg gratings in the same way as used for optical fibers [3].