In our work we have fabricated Bragg grating structures in silicon-on-insulator (SOI) waveguides. SOI waveguides enable integration of both passive and active functions, e.g. thermal, electrical or micromechanical tuning and optical receiving with the gratings. As silicon is a high refractive index material the first order grating period at 1550 nm wavelength is short, only 225 nm, and this period must be precisely controlled. Moreover, the grating must be spatially coherent over its entire length. All this introduces a great challenge for the fabrication techniques used to pattern the grating. Our approach to process gratings in SOI waveguides is based on direct e-beam writing and silicon etching with inductively coupled plasma (ICP). We show results on high aspect ratio Bragg gratings integrated with SOI waveguides with large core size.
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