An All-Polymer Spring Optomechanical Microresonator for Ultrahigh Sensitivity and Wideband Ultrasonic Detection

An ultrahigh sensitivity wideband ultrasonic sensor with an all-polymer spring optomechanical microresonator is presented using two-photon polymerization fabrication technology. The spring optomechanical microresonator is an all-polymer structure based on pentaerythritol tetraacrylate. Its maximum size is only 80 $\mu$ m, which is characterized by miniaturization and rapid manufacturing. A micro-disk and a cylindrical waveguide form the Fabry-Pérot interference cavity with the fiber end surface. The spring structure is used to support the micro-disk and improve the sound sensitivity of the optomechanical microresonator. Experimental results show that its sensitivity is 987.8 times that of the commercial acoustic sensor at 200 KHz, and its acoustic frequency response range is within 50 KHz-400 KHz. The sensor has the advantages of miniaturization, high sensitivity, ease of manufacture and wideband response. It is suitable for partial discharge monitoring in smart grids, measurement of acoustic properties of cells and biological tissues in biomedicine, and medical ultrasound imaging.