EXCITATION OF ACOUSTIC SURFACE WAVES WITH A GRATING-COUPLED GUNN OSCILLATOR

Abstract

Up to 0.25 mW of acoustic surface wave power at 225 MHz have been generated on LiNbO3 with a Gunn oscillator via periodic piezoelectric coupling of the Gunn domain electric fields across an air gap. The coupling periodicity is produced by a metal or dielectric grating on the LiNbO3 surface. The ratio of generated surface wave power Pac to the electrical pulse power is up to 2.5×10−6 for the metal grating and 10−7 for the dielectric grating. The observed dependence of Pac on the number of grating fingers is explained by the degree of phase matching between Gunn domains and acoustic surface waves.