No abstract

In this work, we investigated the optical response of a self-written waveguide (SWW) in detail by heating the structure from room temperature up to 60 °C. Previous results indicated a decrease in the optical transmission with increasing temperature for certain waveguide parameters. Based on new experimental measurements, we have identified material parameters resulting in opposite behaviour. An experimental setup was conceived to verify these results. Hereby, we were able to show that we can adjust material parameters such as refractive index and the corresponding density of the material by adapting the curing time applied during the fabrication of the waveguides. This, in turn, affects the material’s response during the heating process. We showed that a limitation of the external curing time changes the internal conditions of the SWW and the cladding in a manner that the numerical aperture increases with the temperature, which subsequently also results in an increase in the optical transmission. In this study, we explain this unexpected behavior of the SWW and point towards possible future applications.

In this work, we describe a theoretical approach for combined thermal, mechanical and optical simulation and analysis of planar polymer waveguides. We consider a finite element approach for thermal and stress/deformation simulation. Also, a Crank-Nicholson finite difference beam propagation method (CN-BPM) is implemented to perform the optical simulation. The results of the finite element (thermo-mechanical) analysis are coupled with the CN-BPM results to carry out the optical simulation of poly(methyl methacrylate) (PMMA) waveguides as function of temperature. For thermal simulation, a model was designed where a polysilicon microheater was added to the upper cladding of the PMMA waveguides to vary the temperature between 20 • C and 200 • C. Thus, the impact of the induced temperature gradients on the refractive index modulation of the PMMA waveguides and the corresponding change in numerical aperture are obtained. In addition, the temperature gradients influence the beam intensity profiles and the movement of the primary eyes within the optical waveguides, thus, impacting the optical properties. Furthermore, the thermally induced mechanical stress and deformation were calculated for transverse and axial directions. In the next step, validation of the model by systematic experimental studies will be performed. In general, our approach provides a toolbox for more comprehensive multi-physics theoretical analysis of polymer-optical waveguides which, in future, can be extended to more complex and functional structures as required for flexible sensor networks, as example.

Self-written waveguides are an established solution to connect different optical elements with each other. They minimize coupling losses and enable a rigid connection. Furthermore, their characteristics enable a usage as thermal sensing element simultaniously.

This paper focuses on the experimental investigation of pressure drops obtained on different mesh layers setup with the use of Air Filter Performance test rig according to EN 61591 and verification of specially designed test piece and results in quality. Two different mesh sizes and a combination of both were investigated during the experiment. Pressure drops on filters setups were measured, plotted against flow rate, and compared. Test outcome proves that test piece was designed appropriately and pressure drop results obtained on filter setups are aligned with the theory.