Focusing grating coupler in AlGaAs optical waveguide

A focusing grating coupler (FGC) for focusing a guided wave into a spot in free space was fabricated in a III-V semiconductor waveguide for the first time. A FGC of 0.83-mm focal length and 0.5-mm*0.5-mm aperture for an AlGaAs waveguide and 0.83- mu m wavelength was designed and fabricated by electron-beam writing and reactive ion etching. Nearly diffraction-limited focus spot size of 2 mu m and a coupling efficiency of 20% were obtained.<
>