| 摘要 |
PURPOSE:To reduce the number of stages of production for complicated lenses and to make a device small-sized and to improve the efficiency of diffraction to obtain stable operation by constituting the device with only one geodesic lens. CONSTITUTION:The device is so designed that a laser light 7 incident on a plane waveguide 2 from an optical fiber 5 is condensed to an exit 9' which is placed in the position symmetrical to an entrance 9 with respect to the center of a geodesic lens 4, that is, the length from the center of the lens 4 to the laser light entrance 9 or exit 9' is set to a value twice as long as the focal length of the lens 4. Consequently, the laser light 7 is regarded as an approximately parallel light near the center of the lens 4. Similarly, surface acoustic waves (SAW) generated by sectorial comb-shaped electrodes 8 whose centers of sectors are 2f distant from the center of the lens 4 have a plane wave shape near the center of the lens 4 to function as a refractive index density diffraction grating. Thus, only one pulse of SAW is enough for one switch operation, and the efficiency of diffraction is improved considerably. |
