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 300-400 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.