All-photonic SU-8 Variable Optical Attenuator

A polymer-based Micro-optoelectromechanical system (MOEMS) design as a Variable Optical Attenuator (VOA) is presented. It consists on a SU-8 quad-beam structure containing a suspended waveguide aligned to input/output fiber optics. Actuation is achieved by defining photonic-heat transition regions at the anchoring of the mechanical beams. Such actuation points are manufactured by means of a dye-doped SU-8 with a strong absorption at specific wavelengths. When irradiated, the actuation points increase in size, entailing a displacement of the seismic mass, This causes 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 an excellent repeatability and a response time of 1 ms.