| 摘要 |
An optical waveguide device comprises an optical waveguide for guiding an optical wave therethrough, and a grating coupler, which is located on a surface of the optical waveguide and which couples the guided optical wave traveling in the optical waveguide with an external optical wave. The grating coupler is provided with a plurality of bars, the heights h of which vary linearly in the direction along which the guided optical wave travels. The inclination b of the variation of the bar heights h satisfies the condition <IMAGE> where a represents a coefficient which determines a radiation loss coefficient alpha ( alpha =ah2), and L represents the length of the grating coupler, which length is taken in the direction along which the guided optical wave travels. The guided optical wave is radiated very efficiently as an approximately Gaussian beam out of the optical waveguide, or an external optical wave, which takes on the form of a Gaussian beam, is introduced very efficiently into the optical waveguide.
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