PURPOSE: To scan in a high speed with small-sized constitution by providing light shield plates at the projection terminal of an incident optical waveguide and the incidence terminal of a coupled optical waveguide and a DC voltage electrode on the side of the incident optical waveguide, and obtaining convergency with a variable refractive index near the projection terminal of the coupled optical waveguide.

CONSTITUTION: The coupled waveguide 5 has a uniform refractive index distribution up to a length l, and the refractive index decreases at the ratio of the square of the distance from a center axis to obtain convergence at a projection part. When light is incident to the incident optical waveguide 4 while no voltage is applied to an electrode 2, the propagated light is in a state (a) with a complete coupling length L, and all coupled with and propagated to the waveguide 5 and projected with intensity P0 to be convegted at a distance (f). When the light is incident while a DC voltage E0 is applied to the electrode 2, the refractive index in the waveguide 4 varies by electrooptic effect to disconnect the waveguides 4 and 5 from each other, and the projection intensity is 0 as shown by (b), so that no light is projected from the waveguide 5. The projection intensity is controlled by the DC voltage to realize high-speed operation as an optical shutter.