Fabrication of Bragg grating structures in silicon

A fabrication process to realise very short period grating structures in silicon has been developed. The period of a first order Bragg grating operating at a wavelength of 1.55 μm is 230 nm. The grating structures have been directly written to PMMA resist using an electron beam pattern generator. The grating pattern in PMMA is transferred into a silicon dioxide masking layer using plasma etching and into silicon using an inductively coupled plasma etching. An etch depth of 0.6 μm has been achieved. The integration of the grating structure with a large core size silicon-on-insulator rib waveguide is presented.