Observations of the crystal perfection and of surface acoustic waves in lithium niobate

The extended defects in lithium niobate have been studied by X-ray topography using the white radiation delivered by the DCI synchrotron at LURE (Orsay, France). Very few low angle subgrains were observed in slices cut perpendicularly to the X, Y, and Y-45° direction. The high intensity of the synchrotron source has permitted an experimental study of the surface acoustic waves (SAWs) in different filters. Using the time structure of the radiation of the synchrotron and a synchronous excitation, stroboscopic observations were made. It was thus possible to investigate the interactions of the SAWs with the crystal defects, the plate edge, and an acoustic absorbent. The observation of the displacement fields in high-performance filters has revealed interesting properties of apodized transducers and multistrip couplers. It is shown that stroboscopic topography is a good technique for observing and analyzing the wave fields in surface wave devices