Mode conversion in surface-acoustic-wave reflective arrays

We have investigated the possibility of the conversion of surface acoustic waves to other modes in a reflecting-array structure, such as that employed in the reflective-array compressor (r.a.c.). As the angle of incidence on the reflectors is reduced from normal incidence, we find that the mode-conversion possibilities become more restricted. However, for a 45° inclined array of reflectors on LiNbO3, coupling to a strongly piezoelectric pseudo-surface-wave is still allowed. Using metal reflectors, conversion to this mode is observed at frequencies only 19% above the s.a.w. reflection frequency. Comments are made on the relevance of the observations to the fabrication of dispersive filters for pulse-compression systems.