MEMS Fabry–Pérot optical accelerometer employing mechanical amplification via a V-beam structure

•Optical Fabry–Pérot accelerometer employing mechanical amplification.•Eliminates the need for high finesse and difficult fabrication techniques.•V beam structure amplifies motion without pivots and angular rotation.•Analytical expression are derived explaining the action of amplification.

We report a silicon MEMS optical accelerometer based on the Fabry–Pérot interferometer (FPI) principle in which the displacement of the proof mass is mechanically amplified by a V-beam structure prior to transduction. Mechanical amplification allows the sensitivity obtained with a given readout system to be increased without compromising the sensor bandwidth. The FPI cavity in our device is formed between a mirror situated on the V-beam and reflections from the end surface of a cleaved optical fibre. Simple analytical expressions have been derived for the amplification factor of the V-beam structure, in terms of its geometrical parameters, and for its mechanical stiffness which affects the resonant frequency. These were used to design a series of five accelerometers with different mechanical amplification factors which were fabricated and tested. A device having a V-beam angle of 1.9° was capable of detecting accelerations over a dynamic range of 103 between 0.01 g rms and 10 g rms, while a 1.33°angled device achieved the largest amplification of 18.6 ± 6.4.