Evaluation of resonance characteristics of thin film specimen with improved opto-acoustic method

Opto-Acoustic method is a technique evaluating adhesion characteristics of the thin film using optics and acoustic. The test specimen is oscillated by an acoustic transducer and micro-displacement induced by the transducer is detected as a form of interference patterns with Michelson Morley interferometer. And then evaluate resonance characteristics of the thin film by analyzing the interference pattern with Fast Fourier Transform. In this study, we improved our previous optical configuration by better controlling the interferometric light beams. It helps reduce the wave-front curvature in the interference patterns and evaluate the whole thin film specimen. In addition, simulation based on finite element analysis was conducted. An eigenmode study was performed to find eigenfrequencies and mode shapes of a structure. By comparing simulation results and experimental results, we tried to ensure the reliability of Opto-Acoustic method.