Sub-micron integrated grating couplers for single-mode planar optical waveguides

The fabrication of integrated grating couplers for planar optical waveguides is presented. Holographic gratings with spatial period of 300400 nm are produced in photoresist films using a Lloyd's mirror setup. The periodic modulations of the gratings are transferred to soda-lime glass and fused silica substrates through deep reactive-ion etching with a depth of approximately 70 nm. A single-mode waveguide (in the visible region) is created by depositing a film of Al2O3 (180 nm) using an atomic layer deposition process. Characterization of several steps of the device fabrication was done by spectophotometry, atomic force microscope, and measurements of diffraction efficiency.