Acoustic surface wave loss mechanisms on Bi12GeO20 at microwave frequencies

Abstract

Measurements of the acoustic surface wave propagation loss in vacuum on both 001-cut and 111-cut 110-propagating Bi12GeO20 have been made between 200 and 2000 MHz. Approximate f-squared frequency dependence was obtained with a value at 1 GHz of 1.45 dB/μsec. Temperature-dependence measurements illustrate the loss peaks in the vicinity of 50–100 K which are characteristic of Bi12GeO20. The difference in loss between 298 and 4.2 K agrees with over-all room-temperature data indicating attenuation is inherent to the crystal itself and not due to imperfections. Air loading contributes an additional loss of 0.19 dB/μsec at 1 GHz. Beam steering and diffraction considerations illustrate the superiority of the 001 cut over the 111 cut. For linear operation at 320 MHz, surface wave devices on 001-cut 110-propagating Bi12GeO20 should be limited to power densities of 9 mW/mm.