Embossing technique for fabricating surface relief gratings on hard oxide waveguides

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Abstract
Surface relief gratings with 1200, 2400, and 3600 lines/mm on planar SiO2–TiO2 waveguides were fabricated by a combination of a dipcoating method (sol gel process) with an embossing technique. The grating is embossed into a deformable gel film, which by subsequent heat treatment is transformed into an oxide waveguiding film. During the heat treatment the film thickness shrinks to about one-fourth of its value directly after the embossing. Values of the process parameters, e.g., of the embossing pressure, are given with which input and output grating couplers of good quality were fabricated. Measurements of input and output efficiencies are reported; incoupling efficiencies up to ∼28% were obtained.