Twin-bladed microelectro mechanical systems variable optical attenuator

The design and evaluation of a microelectro mechanical systems (MEMS) based variable optical attenuator is reported. The device contains two blades, which are each driven by a separate electrostatic comb microactuator, and move independently to form a variable slit. This device has been fabricated in silicon-on-insulator material which has been back-etched. Electro-mechanical design considerations, including factors to minimise the side instability of the comb drive, are described. Finite element modelling (FEM) of the variable optical attenuator (VOA) is backed up by theoretical results, and the results from the theoretical work verify the findings from the FEM. Optical modelling of the VOA using near field diffraction theory is also reported. Experimentally, the device was driven from 0-34V 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. Optical measurements including wavelength dependent attenuation are also presented.