| 摘要 |
PURPOSE:To reduce the influence of an unnecessary surface acoustic wave upon light in a thin film optical waveguide by canceling the phase shift of light which is phase-modulated with the unnecessary surface acoustic wave by phase modulation by a surface acoustic wave which is generated separately. CONSTITUTION:An optical circuit is formed of thin film optical waveguides 3 and 4 on an optical substrate 1 with piezoelectricity so as to generate two light beams which differ in frequency and incident light is split into two optical waveguide light beams, which are phase-modulated with surface acoustic waves 13a and 15a and shifted in frequency. In this case, the phase modulation for canceling unnecessary periodic phase modulation is imposed with the surface acoustic waves 13b and 15b for correction which are generated by inter-digital electrodes 14 and 16 and the wave fronts of projection light beams which are frequency-shifted do not shift in phase periodically. For example, the spatial phase difference between the surface acoustic waves 27a and 27b is varied from outside to vary the phase modulation state of light propagated in a linear optical waveguide 30 and when the spatial phase difference is set to 180 deg., the periodic phase modulation is canceled. |
