| 摘要 |
PURPOSE:To suppress the attenuation of a surface acoustic wave low in a range where it crosses waveguide light by arranging an IDT (Inter Digital Transducer) which generates the surface acoustic wave at the nearly breadthwise center position of the waveguide light. CONSTITUTION:The IDT 15 is arranged at the nearly breadthwise center position of the waveguide light 13'. The distances where surface acoustic waves 12a and 12b propagated from the part of the IDT 15 in mutually opposite directions cross the waveguide light 13' are about a half as long as the distances where they cross the waveguide light 13' from one end to the other. In this case, as the distances where the surface acoustic waves 12a and 12b cross the waveguide light 13' are shorter and shorter, the absorption of the surface acoustic waves 12a and 12b by the light waveguide 11 is suppressed more and more, so that the extent of the attenuation of the surface acoustic waves 12a and 12b decreases within the range where they crosses the waveguide light 13'. Further, the intensity I of the surface acoustic waves 12a and 12b is maximum at the center par of the waveguide light 13' and diffraction efficiency eta becomes maximum where the light intensity highest. Consequently, the total quantity of the waveguide light 13' after diffraction becomes sufficiently large. |
