title: Testing of Piezo-Actuated Glass Micro-Membranes by Optical Low-Coherence Reflectometry.
abstract: 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.
authors.affiliation: Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli Studi di Pavia, 27100 Pavia, Italy. sabina.merlo@unipv.it.
authors.forename: Sabina
authors.initials: S
authors.lastname: Merlo
authors.affiliation: Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli Studi di Pavia, 27100 Pavia, Italy. itsamonster87@gmail.com.
authors.forename: Paolo
authors.initials: P
authors.lastname: Poma
authors.affiliation: Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli Studi di Pavia, 27100 Pavia, Italy. eleonora.crisa01@universitadipavia.it.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Crisà
authors.affiliation: STMicroelectronics, 20864 Agrate Brianza (MB), Italy. dino.faralli@st.com.
authors.forename: Dino
authors.initials: D
authors.lastname: Faralli
authors.affiliation: STMicroelectronics, 20010 Cornaredo (Mi), Italy. marco.soldo@st.com.
authors.forename: Marco
authors.initials: M
authors.lastname: Soldo
keywords: non-destructive testing; optical low-coherence reflectometry; optical measurements; thin-film piezo-electric actuator