Characterisation of a nanostepper driven optical shutter for application in free-space microoptics

A vertically self-assembled, fibre optic variable optical attenuator (VOA) incorporating a microshutter placed between the end faces of two closely spaced optical fibres is reported. The position of the microshutter with respect to the optical fibre end face was controlled by a nanostepping MEMS motor that was composed of a microactuator array and microsprings. Optical and mechanical tests were performed on the device. It was found that it is possible to obtain a 45 dB dynamic range with an attenuation time of 36 ms. A model of the microshutter was constructed as a plane plate structure with evenly distributed etch holes that are artefacts of the manufacturing process. Geometric and diffraction image analyses were performed and the attenuation characteristic of the system was assessed. It is thus shown that using commercially accessible foundries it is possible to fabricate a high precision VOA for free-space microoptics applications.