Bimorph actuators in thick SiO₂for photonic alignment

Abstract

This paper proposes and tests a design of electro-thermal bimorph actuators for alignment of flexible photonic waveguides fabricated in 16 µm thick SiO 2 . The actuators are for use in a novel alignment concept for multi-port photonic integrated circuits (PICs), in which the fine alignment is taken care of by positioning of suspended, mechanically flexible waveguide beams on one or more of the PICs. The design parameters of the bimorph actuator allow to tune both the initial relative position of the waveguide end-facets, and the motion range of the actuators. Bimorph actuators have been fabricated and characterized. The maximum out-of-plane deflection of the bimorph actuator (with 720 µm-long poly-Si) can reach 18.5 µm with 126.42 mW, sufficient for the proposed application.

Photonic hybrid assembly through flexible waveguides

“…The three degrees of freedom are achieved by: in-plane actuation (T x ) out-of-plane actuation of both actuators (T y ) and tilt of waveguide plane by motion of single out-of-plane actuator (R z ). Demonstrated motion ranges are of the order of several microns [9] implying that the pre-alignment accuracy of the flipchip assembly in the plane normal to the optical axis can be set at typically 2-4 m. Sufficiently high initial placement accuracy in the other directions (T z , R x and R y ) has to be established by the passive pre-alignment, i.e.…”

“…inherent to the PIC fabrication) and, at the same time, provides sufficient motion range for the waveguide alignment tuning after chip assembly [9] . Figure 7 shows the out-of-plane deflection of a waveguide structure when driving the left and right bimorph actuator sets simultaneously with the indicated voltages.…”

Electrothermal Actuators for SiO2 Photonic MEMS

“…In the presented designs, the poly-Si covers the full length of the actuator beams. In other work [ 11 ], we reported on bimorph beams that are partially covered by poly-Si, having the opportunity to, based on the design, control the post-release deformation, as is explained later.…”

“…These design choices are expected to result in a significant post-release deformation. Should the application require it, the post-release deformation can be reduced by means of alternative designs, e.g., partially covering bimorph beams with poly-Si [ 11 ].…”

“…In earlier work, we reported on the initial fabrication results of thermal SiO suspended structures without photonic waveguide cores [ 9 ] and suspended TriPleX structures with waveguide cores [ 10 ]. In addition, we demonstrated TriPleX structures with waveguide cores and simple actuator designs [ 11 ], based on a backside etch approach to release the structures without silicon reinforcement. In the current work, the release of structures relies on front-side etching and benefits from a special silicon reinforcement method, greatly increasing the yield of suspended structures.…”