Thomas Reitberger

Aerosol Jet® printing of optical waveguides

Optical waveguides enable the high speed transmission of data. In this context, Polymer Optical Fibers (POF) offer a great potential for creating an optical network on system level. This paper presents the results of an initial study on Aerosol Jet® printed optical waveguides. Three different kinds of polymer-based inks were printed on thermoplastic and glass substrate materials. The aim was to get basic knowledge of the additive manufacturing of optical waveguides and to investigate fundamental influences of printing parameters and the material combination on the optical (attenuation, refractive index, aspect-ratio) and mechanical (roughness, overspray, adhesion) characteristics. Furthermore, the adhesion of the printed structures on the substrate was tested with regard to a usage of printed waveguides in automotive or electronic applications. In the future, the goal will be to transfer the generated knowledge on flat substrates, into 3D applications. This is basically possible using the Aerosol Jet® Printing technology, as already proven with silver nanoparticle inks on various substrates. By this the freedom of design, the potential of miniaturization and the integration of components can be realized.

Integration of polymer optical waveguides by using flexographic and aerosol jet printing

As a tribute to the continuously increasing volume of data traffic, optical waveguides have become a serious alternative to electrical circuitries. The potential of precise spaceresolved strain measurements or the capacity to transmit very large amounts of data are two examples of the beneficial use of optical systems. Apart from the general advantages of the optical signal line, like high electromagnetic compatibility, usage in explosive atmosphere or the reduced weight compared to copper cables, modern technologies make use of the possibilities to integrate optical waveguides into structural components. The printing of polymer optical waveguides is part of the current research in functional printing technology. Optimizing the transmission quality and the resolution are key objectives to establish integrated optical data transmission in industry. The manufacturing of multimode waveguides presented in this work is accomplished by a combination of two printing processes. Before producing the optical waveguide itself, using Aerosol Jet Printing, pre-conditioned areas with either hydrophobic or hydrophilic behavior are generated on flexible substrates with an adapted flexographic printing mechanism. This two-stage process allows for the fabrication of step index waveguides featuring parabolic cross sections with minimum widths down to 10 μm and aspect ratios of about 0.3. Conditioning the substrate, which itself forms the bottom cladding, provides a low surface roughness of the optical core. This paper shows the latest results of printing polymer optical waveguides, focusing on actual challenges and optical transmission quality.

The future of short-range high-speed data transmission: printed polymer optical waveguides (POW) innovation, fabrication, and challenges

One of today’s megatrends in the industrial environment is additive manufacturing. Faster prototyping, customized products like hearing devices, integrated functions like heatsinks and many other opportunities are offered by this technological development. The opportunity of using different materials and build up 3-D structures is virtually infinite. Another one is the digitalization of almost any product to build up a smart world. This trend leads to a tremendously rising amount of data to be transferred from one place to another. If a wireless transmission is not possible and if the distance is over 100 m glass fiber is the fastest and most secure way for these requirements. In case of most short-range applications up to 100 m primary copper cables or circuit paths are in use because the electrical data transfer is well known. The limited bandwidth of copper asks for new inventions to meet the demands of tomorrow. Regarding both megatrends, the solution for this upcoming bottleneck could be 3-D printed photonic packages. This paper shows a new and innovative way for the customized fabricating of short-range data transmission networks. By Aerosol Jet Printing (AJP) the so called polymer optical waveguides (POW), it is possible to build up 3-D printed light guiding structures with low attenuation on almost any three-dimensional surface. The main advantages of the here presented research are high flexibility, low weight and low costs. After three years of intensive studies the most important key facts (machine settings, geometry, performance) are summarized in this publication.

Important parameters of printed polymer optical waveguides (POWs) in simulation and fabrication

In this paper, polymer optical waveguides (POWs), fabricated by using flexographic printing for printing conditioning lines onto polymethylmethacrylate (PMMA) foil substrate material and Aerosol Jet Printing for producing the core and cladding of the waveguide, are characterized by using Monte Carlo raytracing for the scattering process. This method offers the opportunity to simulate the propagation of light, which are traced through the produced POWs. In the first step, the surface roughness of all optical materials, which are involved in the fabrication process of the POWs, are measured. The roughness measurement of substrate, core and cladding material is necessary to interlink the surface roughness (Monte Carlo scattering model) with a non-sequential raytracing method. Not only the surface of each material is investigated, but also the roughness measurement of the interlayer between the printed core and cladding material is examined. To build up the complete manufacturing technology virtually, also the process parameters of the printing need to be investigated. The results of the tracing must be a value of the attenuation of a simulated printed POW to give the designer a feedback about the optical quality of the waveguide before the printing process. This project is part of the DFG (the German Research Foundation) founded research group OPTAVER where the goal is to build up the whole manufacturing process, from the CAD, over the simulation, to the fabrication process and coupling of such printed POWs.

Improving partial wetting resolution on flexible substrates for application of polymer optical waveguides

Abstract. Considering the increasing amount of data for communication and infotainment applications, fabrication of optical networks and bus systems is a challenging task for production engineering. A two-step manufacturing process for polymer optical waveguides is presented. By improving the highly efficient flexographic printing technology by laser functionalization of the printing tool in combination with a subsequent spray application, high-quality waveguides are accomplished. By adjusting the resulting surface energy of the foil substrate in the first fabrication process, the spray application achieved high-aspect ratio waveguides with a low attenuation of 0.2  dB/cm at 850 nm.

Asymmetric Optical Bus Coupler for Interruption-Free Short-Range Connections on Board and Module Level

In this paper, we present a bidirectional interruption-free multimode waveguide coupler for optical bus systems on board and module level. The principle is based on directional core–core coupling and allows for adjustable coupling powers by tuning the overlap area. By adding a bending to one of the coupling partners, it is possible to obtain specific asymmetric coupling rates depending on the coupling direction (module to bus or vice versa). The proposed approach is extensively analyzed by optical simulation (beam propagation method) and measurements including experiments on the attenuation, the coupling rate, and the bit rate performance.

Approach for the production chain of printed polymer optical waveguides–an overview

Research for new production chains in the field of waveguide fabrication is a challenging task. Realizing a cost efficient manufacturing process allows integrating optical data communication in arbitrary structures, for example, the wing of an airplane or the body of a car. The production chain described in this paper contains the design, simulation, and fabrication process of printed polymer optical waveguides (POWs).

Printing polymer optical Waveguides on conditioned transparent flexible Foils by using the Aerosol Jet Technology

The optical data transfer is considered as the future of signal transfer due to its various advantages compared to conventional copper-based technologies. The Aerosol Jet Printing (AJP) technology offers the opportunity to print materials with high viscosities, such as liquid transparent polymer adhesives (epoxy resins), on almost any possible substrate material and even in third dimension. This paper introduces a new flexible and comparatively cost-effective way of generating polymer optical waveguides through AJP. Furthermore, the conditioning of the substrate material and the printing process of planar waveguides are presented. In the first step, two lines with hydrophobic behavior are applied on foil material (PMMA, PVC, PI) by using a flexographic printing machine. These silicone based patterns containing functional polymer form barriers for the core material due to their low surface energy after curing. In the second step, the core material (liquid polymer, varnish) is printed between the barrier lines. Because of the hydrophobic behavior of the lines, the contact angle between the substrate surface and the liquid core material is increased which yields to higher aspect ratio. The distance between the barrier lines is at least 100 μm, which defines the width of the waveguide. The minimum height of the core shall be 50 μm. After UV-curing of the core polymer, the cladding material is printed on the top. This is also applied by using the AJP technology. Various tests were performed to achieve the optimal surface properties for adequate adhesion and machine process parameters.