Suspended photonic waveguide arrays for submicrometer alignment

This paper presents a new alignment concept for the alignment of multichannel photonic intergrated circuits (PICs) using flexible photonic waveguides on one of the PICs that are positionable by integrated micro electro mechanical system (MEMS) actuators. The concept aims for high precision and high degree of assembly process automation. The proposed concept includes pre-alignment of both PICs on a common substrate followed by fine-alignment using the on-chip flexible waveguides and MEMS functionality. This paper introduces the alignment approach and reports on the development and fabrication of suspended and mechanically flexible photonic waveguides. Single suspended waveguide beams and suspended arrays with two and four coupled parallel waveguide beams of different lengths (250 µm to 1000 µm) and different widths (18 µm to 34 µm) are designed and fabricated. After fabrication, waveguide beam fracturing is observed. The fabrication process has been extended by an additional under-etching step in order to reduce beam fracturing. The static out-of-plane deflection of the fabricated devices follows a specific profile with a dominating upward curvature resulting in a measured maximum out-of-plane deflection of 2 % of the length. The beam stiffness of the fabricated devices is measured and proves to be within the available force of microactuators. 1