Dielectric elastomers (DEs) have received significant attention for their good performance among different smart material transducers. This study demonstrates the feasibility of fabricating dielectric elastomer actuators (DEAs) using exclusively inkjet printing technique. The manufactured unimorph bending cantilevers are composed of a polydimethylsiloxane (PDMS) active layer, sandwiched between two compliant electrodes, and printed onto a thin polyimide (PI) substrate. This study addresses the key fabrication challenges associated with inkjet printing such a layered actuator structure. This entails the consistent printing of the Ag electrodes on the smooth PI substrate, a PDMS layer on the Ag electrodes, the Ag electrodes on the smooth PDMS surface, and the respective steps of processing and curing. The fully inkjet-printed DEAs exhibited a maximum tip displacement of 36 μm in quasi-static operation (1 kVpp) and 12.8 μm in resonant operation (50 Hz, 800 Vpp). This is the first time that inkjet-printing has been employed to print an entire dielectric elastomer actuator, broadening the outlooks to develop innovative devices that base on smart material transducers.
Fully automated, high precision, cost-effective assembly technology for photonic packages remains one of the main challenges in photonic component manufacturing. Next to the cost aspect the most demanding assembly task for multiport photonic integrated circuits (PICs) is the high-precision (±0.1 μm) alignment and fixing required for optical I/O in InP PICs, even with waveguide spot size conversion. In a European research initiative – PHASTFlex - we develop and investigate an innovative, novel assembly concept, in which the waveguides in a matching TriPleX interposer PIC are released during fabrication to make them movable. After assembly of both chips by flip-chip bonding on a common carrier, TriPleX based actuators and clamping functions position and fix the flexible waveguides with the required accuracy.
This paper reports on the progress related to a multichannel photonic alignment concept, aiming for sub-micrometer precision in the alignment of the waveguides of two photonic integrated circuits (PICs). The concept consists of two steps: chip-to-chip positioning and chip bonding provide a coarse alignment after which waveguide-to-waveguide positioning and fixing result in a fine alignment. For the waveguide-to-waveguide alignment, an alignment functionality is developed and integrated in one of the PICs, consisting of mechanically flexible waveguides and MEMS actuators. This paper reports on the fabrication and characterization of a mechanically flexible waveguide array that can be positioned by two out-of-plane actuators.
Thermal actuators are integrated with mechanically flexible waveguide beams to enable positioning them with high precision. By adding a poly-Si pattern on top of SiO2 beams, an out-of-plane bimorph actuator can be realized. An analytical model enables estimating the curvature and the deflection of a single bimorph beam. Acquiring a small initial deflection while having a large motion range of the actuator proves to have conflicting demands on the poly-Si/SiO2 thickness ratio.
In this paper, we show that suspended waveguide arrays with integrated alignment functionality have an initial deflection- they curl up- due to residual stress in the materials. The actuators can be operated using a driving voltage between 0V to 45V, corresponding to ~50mW. Using higher voltages brings the risk of permanently changing the material properties of the heaters. The actuators can accomplish an out-of-plane crossbar translation up to 6.5 μm at ~50mW as well as a rotation around the propagation direction of the light ranging from -0:1° to 0.1°. At a constant actuation power of ~50mW, the crossbar shows a drift in vertical deflection of 0.16 μm over a time of 30 min.
This paper reports on the progress related to a multichannel photonic alignment concept, which aims to achieve submicrometer alignment of the waveguides of two photonic integrated circuits (PICs). The concept consists of two steps: chip-to-chip positioning and fixing provide a coarse alignment after which waveguide-to-waveguide positioning and fixing result in a fine alignment. For the waveguide-to-waveguide alignment, mechanically flexible waveguides are used. Positioning of the waveguides is performed by integrated MEMS actuators. The flexible waveguides and the actuators are both integrated in one of the PICs. This paper reports on the fabrication and the mechanical characterization of the suspended waveguide structures. The flexible waveguide array is created in a PIC which is based on TriPleX technology, i.e. a silicon nitride (Si3N4) core encapsulated in a silicon dioxide (SiO2) cladding. The realized flexible waveguide structures consist of parallel cantilevered waveguide beams and a crossbar that connects the free ends of the waveguide beams. The fabrication of suspended structures consisting of a thick, i.e. 15 µm, TriPleX layer stack is challenged by the compressive mean stress in the SiO2. We have developed a fabrication method for the reliable release of flexible TriPleX structures, resulting in a 96% yield of cantilever beams. The realized suspended waveguide arrays have a natural out-of-plane deformation, which is studied using white light interferometry. Suspended waveguide beams reveal a downward slope at the base of the beams close to 0:5_. In addition to this slope, the beams have a concave upward profile. The constant curvature over the length of the waveguide beams is measured to range from 0:2 µm to 0:8 µm. The profiles measured over the length of the crossbars do not seem to follow a circular curvature. The variation in deflection within crossbars is measured to be smaller than 0:2 µm.
This paper proposes and tests a design of electro-thermal bimorph actuators for alignment of flexible photonic waveguides fabricated in 16 µm thick SiO2. 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 126:42mW, sufficient for the proposed application.
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.
Passive alignment of photonic components is an assembly method compatible with a high production volume. Its
precision performance relies completely on the dimensional accuracies of geometrical alignment features. A tolerance
analysis plays a key role in designing and optimizing these passive alignment features. The objective of this paper is to
develop a systematic approach for conducting such tolerance analysis, starting with a conceptual package design, setting
up the tolerance chain, describing it mathematically and converting the misalignment to a coupling loss probability
distribution expressed in dB. The method has successfully been applied to a case study where an indium phosphide (InP)
chip is aligned with a TriPleX1 (SiO2 cladding with Si3N4 core) interposer via a silicon optical bench (SiOB).
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