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.