| 摘要 |
PURPOSE:To move a condensing point at the time of tracking or focusing without using an outside changing means by forming a diffraction grating in an optical waveguide by means of a surface acoustic wave by a surface acoustic wave element, changing the driving signal frequency of the surface acoustic wave element and controlling a condensing position. CONSTITUTION:The surface of a substrate 10 which has a piezoelectric effect like a single crystal LinNbO3, etc., is provided with the two-dimensional optical guidewave and a pair of interdigital electrodes 20 which generates the surface acoustic wave is formed on its one side. When the electrode 20 is driven by a driving signal generation circuit 22, the index of refraction is raised corresponding to surface wave propagation so that the diffraction grating 24 is formed in the optical waveguide 12 by an acoustic optical effect by periodic roughness and laser light which propagates the optical waveguide 12 from a lazer diode 18 is condensed on a point A outside the optical waveguide 12 by the grating 24. The driving signal enables the frequency to be periodically swept, a condensing point position to be controlled corresponding to the frequency and the condensing position to be desirably moved at the time of tracking or focusing without using the outside changing means. |
