3D Terahertz Detection of Internal Defects Within Polymer Materials Using a Thermomechanical Performance-Enhanced Bi-Material Microcantilever FPA

This paper proposes a 3D terahertz (THz) detection technology for the characterization of hidden defects within polymer materials based on a thermomechanical focal plane array (FPA) that integrates THz metamaterial absorbers (MAs) on microcantilevers. By optimizing the SiN<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> thickness in the MAs and the microcantilever legs, the microcantilever FPA demonstrates an ultra-sensitive thermomechanical response, with a thermomechanical sensitivity of 8.13 μm/K and a response time of 25 ms. An optical readout system was developed to capture visible light reflected from the Au mirror layer, simultaneously acquiring the deflection of all microcantilever pixels and converting it into a grayscale image. Utilizing multi-angle THz projection data and a tomographic image contour extraction algorithm, the 3D structures of internal defects within polymer materials were successfully reconstructed.