All-polymer optothermal-actuated MOEMS variable optical attenuator

This paper presents the design, fabrication and characterization of all-optical polymer-based Micro-optoelectromechanical system (MOEMS) Variable Optical Attenuator (VOA). It consists of an SU-8 quad-beam structure and a suspended waveguide aligned to input/output fiber optics. Actuation is achieved by defining dye-doped SU-8 structures on the mechanical beams. Specific wavelengths focused on such structures have a strong absorption resulting in a heating and, straightforwardly, an expansion of the dye-doped SU-8. This entails a displacement of the seismic mass causing a misalignment (i.e. an increase of the coupling losses) between the waveguides and the input/output fiber optics. Experimental results have validated this approach, by showing the effect of the pumping power on the optical losses, with a slope of 0.17 dB/mW.