title: A laser-activated MEMS transducer for efficient generation of narrowband longitudinal ultrasonic waves.
abstract: In this paper, we demonstrate an optically powered microelectromechanical system (MEMS) transducer. It was designed and fabricated using MEMS techniques, and can generate narrowband ultrasonic bulk waves from a broadband laser excitation pulse with high efficiency. The transducer is a two-mask-level MEMS device with a microdisk seated on a microstem. When a laser pulse is incident on the disk center, a resonant flapping motion of the disk is actuated because of the thermomechanical interaction between the absorbing and non-absorbing parts of the disk, coupling a narrowband longitudinal bulk wave propagating along the axis of the stem into the sample. Finite element (FE) methods were used to simulate the generated ultrasound; the results agree well with experimental measurements. Experiments with the fabricated transducers have shown that narrowband ultrasound with a high SNR/amplitude was generated successfully; compared with normal thermoelastic generation, ultrasound with at least 5 times higher amplitude can be achieved by an optimized MEMS transducer. The transducer is inexpensive, compact, and simple to use.
authors.affiliation: Electrical Systems and Optics Research Division, University of Nottingham, Nottingham, UK. xuesheng.chen@nottingham.ac.uk
authors.forename: Xuesheng
authors.initials: X
authors.lastname: Chen
authors.forename: Theodosia
authors.initials: T
authors.lastname: Stratoudaki
authors.forename: Steve D
authors.initials: SD
authors.lastname: Sharples
authors.forename: Matt
authors.initials: M
authors.lastname: Clark
mesh_terms: D004867:Equipment Design; D020342:Finite Element Analysis; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D014159:Transducers; D014465:Ultrasonics / Q000379:methods*