High-Performance Focusing Grating Coupler Fabricated by Electron-Beam Writing

Focusing grating couplers (FGC's)1, 2 are an attractive component for integrated optics, since they have applications as thin film waveguide to LD or fiber couplers and can also be the key component for the future integration of optical disc pickup devices. The FGC's fabricated by the holographic technique1, however, have limited application since they exhibit large aberration due to the difference in wavelength between the fabrication light and the coupling light. By the electron-beam (EB) writing, aberration-free FGC's for use at arbitrary wavelength can be fabricated2. In this paper, we present a high-efficiency diffraction-limited focusing grating coupler fabricated by the EB writing.