This paper analyzes an approach for additively manufacturing polymer optical waveguides. The production process includes flexographic printing of conditioning lines (5 μm height) on a substrate, which are used as guiding barriers in the subsequent printing of the optical core. The core is additively printed (up to 50 μm in height) with an aerosol jet printer, filling the gap between the conditioning lines. The conditioning lines do not only enhance the contact angle of the polymer, which results in a higher cross section of the waveguides, but also improve the straight edges of the printed waveguides. We show that the quality of the conditioning lines is directly correlated to the waviness of the waveguides. Consequently, the analyses of the waviness of the conditioning lines classifies the quality of the fabricated waveguides. However, the waviness of the waveguides can also be considered in optical simulations. In this paper we show how we derive a waveguide model with waviness by fitting a single sine function onto the topological data of the conditioning lines. With this model a variation of the waviness can easily be simulated and goals for fabrication can be set. With the simulations it is possible to verify that the measured waviness (period of 559.5 μm and an amplitude of 4.99 μm) does not affect the optical quality of the waveguides.
A novel coupling approach with specific coupling ratios depending on the coupling direction (optical bus to electrooptical device and vice versa) is presented. According to that, an asymmetric optical bus coupler (AOBC) is obtained, where a high amount of light is coupled from a device/module into the optical bus, whereas the ratio in the opposite direction is significantly smaller to keep enough energy in the bus for later coupling. This is realized without any filters by a specific bending of the waveguides. Hence, an up to four times higher coupling ratio in the module-to-bus direction is achieved compared to the opposite direction at the same junction. In contrast, current coupling schemes have a 1:1 coupling, waveguides are interrupted or filters are used. In this paper we investigate the influence of the waveguide manufacturing technology on the coupling performance. The standard photolithographic waveguides with rectangular cross-sections are compared to Aerosol Jet printed waveguides with circular segment cross-sections. Furthermore, we monitored the coupling for several days to get results on the stability. The results show a fluctuation of about ± 20 % for the printed waveguides and about ± 5 % for the photolithographic ones.
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.
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.
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.
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.
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