Testing of Piezo-Actuated Glass Micro-Membranes by Optical Low-Coherence Reflectometry

• Main Authors: Sabina Merlo, Paolo Poma, Eleonora Crisà, Dino Faralli, Marco Soldo
• Format: Article
• Language: English
• Published: MDPI AG 2017-02-01
• Series: Sensors
• Subjects: optical low-coherence reflectometry; optical measurements; thin-film piezo-electric actuator; non-destructive testing
• Online Access: http://www.mdpi.com/1424-8220/17/3/462

In this work, we have applied optical low-coherence reflectometry (OLCR), implemented with infra-red light propagating in fiberoptic paths, to perform static and dynamic analyses on piezo-actuated glass micro-membranes. The actuator was fabricated by means of thin-film piezoelectric MEMS technology and was employed for modifying the micro-membrane curvature, in view of its application in micro-optic devices, such as variable focus micro-lenses. We are here showing that OLCR incorporating a near-infrared superluminescent light emitting diode as the read-out source is suitable for measuring various parameters such as the micro-membrane optical path-length, the membrane displacement as a function of the applied voltage (yielding the piezo-actuator hysteresis) as well as the resonance curve of the fundamental vibration mode. The use of an optical source with short coherence-time allows performing interferometric measurements without spurious resonance effects due to multiple parallel interfaces of highly planar slabs, furthermore selecting the plane/layer to be monitored. We demonstrate that the same compact and flexible setup can be successfully employed to perform spot optical measurements for static and dynamic characterization of piezo-MEMS in real time.