Abstract

Focusing grating coupler (FGC), which has a function of coupling the planer guided wave and the spherical free space wave, will play a key role in optical integrated circuit devices. FGC is realized by forming a specific grating corrugation with chirp and bend structure on a waveguide. For fabricating FGC corrugation, either holographic exposure method⁽¹⁾ or electron beam lithography⁽²⁾ have been employed. Since exactly tuneed wavelength laser source and non-spherical wave-front adjuster are required depending on the guided wave parameters, an aberration free FGC is difficult to achieve by holographic techniques. Computer-controlled electron beam writing technique seems to be more promising, because the appropriate electron-beam trace on the substrate is basically achievable for each waveguide by adjusting the writing guided wave parameters such as refractive index of the waveguide and the wavelength of light source. In fact, FGC (1x1mm², f=2mm) with spot size of 1.3 times of the diffraction limited one has been realized by T. Suhara et. al.⁽²⁾

© 1989 Optical Society of America