Investigation of the features of elastic wave generation and propagation in Bi12GeO20 crystals using the acousto-optic method

摘要

Acousto-optic methods are widely used not only in devices and systems for radio and optical signal processing, but also for studying physical properties of various materials. The paper presents the results of the investigation of the "non-resonance" (due to native piezoelectric effect) generation of elastic waves at super high frequencies in the Bi12GeO20 crystal, using the acousto-optic method. Acoustic field patterns are visualized in various crystal cuts, including the "degenerated" acoustic mode in the [111] direction in the crystal. Conditions are discussed under which acoustic modes and directions exist with the "self-collimation" effect (abnormally low power spread of acoustic wave). Quantitative estimation of collimation quality is made for various conditions. Experimental characteristics of high-order harmonics generation processes appeared due to elastic non-linearity of the material are found. Basing on the experimental data, some parameters of the elastic non-linearity are evaluated.