Design and evaluation of a MEMS optical chopper for fibre optic applications

The design and evaluation of a MEMS-based chopper for optical measurements is reported. The overall dimensions of the chopper, including the microactuators and micromechanical suspension, are 1200×1200 μm making it very compact. The comb-actuator driven chopper, designed for use in conjunction with fibre optics, has been fabricated in silicon-on-insulator material which has been back-etched to create an optical path through the thickness of the substrate. General electro-mechanical design considerations, including factors to minimise the side instability of the comb drive, are described. Finite element modelling (FEM) of the chopper is backed up by simple theoretical results, and the results from the theoretical work verify the findings from the FEM. Optical modelling of the chopper is also reported. Experimentally, the device was driven from 0-34 V DC to measure its static characteristics. For dynamic characterisation, the device was operated from 0-28 V AC and its fundamental resonant frequency was measured to be 3 kHz. Experimental evaluation of the device characteristics are shown to closely match the theoretical predictions.