Quad beam polymeric optomechanical systems

Abstract

The design, simulation, fabrication and characterization of two SU-8 based microoptoelectromechanical systems (MOEMS) are presented in this paper: an optical accelerometer and a variable optical attenuator (VOA). Both devices consist on a quad-beam polymer structure and can be fabricated with a simple technology, requiring only two photolithographic steps. In order to overcome the fibre optics positioning, self-alignment structures have been integrated on the devices. Working principle of both devices is based in the modulation of the optical losses (when an acceleration or voltage is applied at the accelerometer or the VOA, respectively). In order to achieve the optimal behaviour, several quad beam configurations have been studied by means of mechanical and optical simulations. An optical sensitivity of 16.58 dB/g has been estimated for the optimal configuration of the accelerometer. The experimental results show a good agreement, with measured optical sensitivities of 13.1 dB/g and 17.5 dB/g for negative and positive accelerations, respectively. On the other hand, the VOA has been electrothermally actuated, taking advantage of the high thermal expansion coefficient (CTE) of the SU-8, to achieve high optical attenuation (20 dB) with low power consumption (12mW).