Abstract
Focusing waveguide grating couplers (FWGCs) play important roles in many integrated-optic devices, such as the integrated-optic disk pickup device[1], Such a FWGC can be evaluated in terms of: (i) coupling efficiency as a grating coupler and (ii) focusing performance as a focusing lens. Fabrication of diffraction-limited focusing waveguide grating couplers by electron-beam lithography has been previously reported by other researcherd[2]. However, high focusing performance as well as high coupling efficiency is of great importance for obtaining high signal-to-noise ratio in a practical device. The coupling efficiency theoretically obtained so far is around 60% when using a buffer layer reflector[1]. The other possible method to achieve higher efficiency is to utilize a multi-layered high-reflectivity dielectric stack[3], providing a radiation directionality of greater than 95%. In this paper, a high efficiency focusing waveguide grating coupler using a new waveguide grating structure is proposed, designed and fabricated by direct-write electron beam lithography.
© 1996 Optical Society of America
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