Weak gratings in silicon-on-insulator for spectral filters based on volume holography.

We demonstrate integrated holographic grating filters, that can be designed toward any desired target spectrum. A straightforward design method transforms this target spectrum into a weak effective refractive index variation. The filters are implemented in high-contrast silicon-on-insulator by modulating the width of the shallow etched sides of a ridge waveguide. Measurements show that this is a promising approach to integrate flexible and versatile filters on photonic chips to enable more complex applications.