Raetz Samuel, Dehoux Thomas, Perton Mathieu, Audoin Bertrand
Université de Bordeaux, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5295, I2M, 351 cours de la Libération, F-33400, Talence, France.
J Acoust Soc Am. 2013 Dec;134(6):4381. doi: 10.1121/1.4828825.
The symmetry of a thermoelastic source resulting from laser absorption can be broken when the direction of light propagation in an elastic half-space is inclined relatively to the surface. This leads to an asymmetry of the directivity patterns of both compressional and shear acoustic waves. In contrast to classical surface acoustic sources, the tunable volume source allows one to take advantage of the mode conversion at the surface to control the directivity of specific modes. Physical interpretations of the evolution of the directivity patterns with the increasing light angle of incidence and of the relations between the preferential directions of compressional- and shear-wave emission are proposed. In order to compare calculated directivity patterns with measurements of normal displacement amplitudes performed on plates, a procedure is proposed to transform the directivity patterns into pseudo-directivity patterns representative of the experimental conditions. The comparison of the theoretical with measured pseudo-directivity patterns demonstrates the ability to enhance bulk-wave amplitudes and to steer specific bulk acoustic modes by adequately tuning light refraction.
当弹性半空间中光的传播方向相对于表面倾斜时，由激光吸收产生的热弹性源的对称性会被打破。这会导致压缩声波和剪切声波的指向性图案出现不对称。与传统的表面声源不同，可调谐体声源使人们能够利用表面的模式转换来控制特定模式的指向性。文中提出了随着光入射角增加指向性图案的演变以及压缩波和剪切波发射优先方向之间关系的物理解释。为了将计算出的指向性图案与在平板上进行的法向位移振幅测量结果进行比较，提出了一种将指向性图案转换为代表实验条件的伪指向性图案的方法。理论伪指向性图案与测量结果的比较表明，通过适当调整光折射，可以增强体波振幅并控制特定的体声模式。
