SUMMARYIf a surface acoustic wave is excited on the substrate when an optical thin-film waveguide is fabricated on it, the photoelasticity of the thin film is found to nearly double. The present research investigates both theoretically and experimentally this enhancement of photoelasticity by surface acoustic waves. The structure used is (Ta 2 O 5 /SiO 2 /128°YX-LiNbO 3 ) with a thin-film waveguide made of tantalum pentoxide (Ta 2 O 5 ), the most stable among the oxides. A photoacoustic deflector is fabricated in which both the TE and TM modes can propagate. From the deflection efficiency, the photoelasticity (p 11 , p 12 ) is estimated. It is found that p 11 is increased by a factor of 2.27 and p 12 by a factor of 2.19. As an application of this phenomenon, an optical deflector driven at low power for the TM guided mode is realized. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(5): 4654, 2001

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By depositing a thin film on a substrate in which a standing surface wave is excited, we fabricated a phase grating in which variations in the film thickness as well as the refractive index occurred at half the wavelength of the surface acoustic waves. As no such phenomenon has been reported until now, its application for optical elements is expected.

Controlling chaos of density fluctuations observed in electron cyclotron resonance (ECR) plasma is carried out using the timedelayed auto synchronization (TDAS) method introduced by Pyragas. Since the TDAS method, which is a sort of feedback system, requires a feedback signal, the input power of microwaves for ECR discharge is modulated by signals of frequency (<30 kHz) based on the ion-saturation current indicating the electron density. Fluctuations caused by the flute instability reach the chaotic state when the microwave power is increased. It was found that when the TDAS method is applied to the chaotic state, the chaotic state transitions to the periodic state and the correlation dimension changes from a non integer value to an integer value.