In-plane positioning of flexible silicon-dioxide photonic waveguides

This paper describes the design, fabrication and characterization of an in-plane positioning system within a thick (16 micrometers) silicon dioxide photonic-material stack. This is part of a proposed novel photonic alignment scheme, targeting at highly-automated assembly and high-precision alignment of multi-port photonic chips. Creating such functionality in thick silicon dioxide is challenging because of its low coefficient of thermal expansion, as well as the stresses present in the material. A design is proposed which addresses both challenges, and which in fact makes positive use of the present stress. The in-plane positioning system combines an electrothermal chevron actuator and a lever mechanism, aiming to achieve several micrometer displacement. The lever structure is proposed to amplify the motion of the chevron actuator. The shuttle of the chevron actuator and the lever are provided with a set of hooks. The hooks engage during the fabrication of the structure, because of the stress-induced retraction of the chevron actuator. With this design, a robust fabrication yield was achieved. The characterization work includes analyzing the engagement between the hook and chevron actuator, and the in-plane displacement with the lever enhancement.