High rectification in a broadband subwavelength acoustic device using liquid crystals

Abstract

Acoustic diodes can be relevant to improve the audible comfort of indoor environments or to provide better ultrasound images. However, such diodes are usually based on nonlinear materials and microstructured and nanostructured asymmetries, making it difficult to produce them. We present in this article a high rectification acoustic device based on the liquid crystal 5CB, forming an escaped radial disclination kept in a conical frustum tube. Solving the wave equation numerically for this system, we observe that the lack of spatial inversion symmetry along the device's axis produces rectifications up to 1300% for a continuous frequency range from 20 Hz to 20 kHz. We performed a study varying the wave frequency, the tube geometry, and the liquid crystal orientation to identify values that produce the maximum acoustic rectification. Because these liquid crystals have been known for a long time and have well-known manipulation techniques, our results have practical significance in designing novel liquid crystal devices, such as acoustic rectification films.