Fourier-transform-limited performance of a lithographically scribed planar holographic Bragg reflector

Planar holographic Bragg reflectors (HBRs) are computer-generated two-dimensional (2-D) slab-waveguide-based refractive-index gratings. HBRs provide the spectral filtering function of fiber Bragg gratings but-enabled by the 2-D slab waveguide geometry-add the capability to spatially route signals. Here, we report on a silica-on-silicon-based focusing HBR providing 17 GHz, essentially Fourier-transform-limited, spectral resolution. This result comprises the first time deep ultraviolet projection lithography is successfully applied to the fabrication of a 2-D Bragg reflector on the centimeter scale. The 2-D Bragg filter occupies a compact 0.3 cm² footprint and provides diffraction-limited spatial input-output beam mapping.