Fabrication technology for improving pattern quality in focusing waveguide grating coupler manufacture

Abstract

This paper presents several exposure strategies that greatly improve pattern quality in delineating curved gratings in the nanometer range. A focusing waveguide grating coupler (FWGC) was not fabricated by the ‘continuous path control’ writing strategy but by a single-step e-beam lithography system with conventional exposure mode. The exposure strategies proposed are to match the address grid, which is an exposure scan direction, to the grating period, and also to apply the grating period to an integer multiple of the address grid resolution (5 nm). The grating pitch period and aperture feature size of the FWGC designed and fabricated here are 384.3–448.2 nm and 0.5×0.5-mm 2, respectively. The presented fabrication method will also reduce processing time and improve grating pattern quality through address grid resolution, grating direction, pitch size and shapes in the e-beam exposure. Here our investigations concentrate on the design and efficient fabrication of the FWGC for coupling from slab waveguide to a spot in free space.