The concept of quantum nanolaminates (QNL) postulates the decoupling of band gap and refractive index, which in regular dielectric materials is linked. We will show that the quantization effect can be observed in nanolaminate structures of the material combinations Ta2O5-SiO2 and amorphous silicon-SiO2, which were deposited by magnetron sputter deposition. These nanolaminates were characterized by a variety of different methods, which confirmed the layer structure in the nanometer range and the shift of the absorption edge to shorter wavelength. Furthermore, the use of the QNL as the high refractive index material in optical interference coatings was successfully demonstrated in anti-reflection and long pass filter coatings.
Quantization effects in nanolaminate structures of oxide materials were proposed and experimentally demonstrated only recently. In this paper we will investigate the material combinations of Ta2O5-SiO2 and amorphous silicon-SiO2 deposited by magnetron sputtering and show that the quantization effect is observed in both materials. We will describe the deposition process and demonstrate the tunability of the refractive index and the bandgap energy. Quantized nanolaminates (QNL) composed of Ta2O5-SiO2 in combination with SiO2 were used as high and low refractive materials in optical interference coatings forming an antireflection and a mirror coating, whereas QNL with aSi-SiO2 as the high index material were used in a log pass filter with edge at 720nm. All designs could be deposited successfully with close match to the design. The aSi-SiO2 based filter showed a blocking range throughout the visible spectrum whereas a comparable filter based on SiO2-TiO2 only blocked 500-700nm.
KEYWORDS: Coating, Error analysis, Camera shutters, Optical simulations, Neodymium, Global system for mobile communications, Data processing, Tolerancing, Signal processing, Reflectivity
Various types of optical monitoring systems are established in industry. They range from single wavelength, over monochromatic to broadband monitoring to calculate a monitoring signal, which allows to terminate each layer in a filter at the required thickness. State of the art monitoring systems offer the capability of monochromatic and broadband monitoring in a single device. With these technologies available, the question arises how to combine these monitoring strategies for a specific application in a way, which leads to accurate coating results with the least sensitivity to production errors and thus to the highest yield. To answer this question without the need to perform costly coating runs, we developed a software tool, which mimics all the monitoring features of Evatec’s GSM optical monitoring system. Additionally, the software is able to disturb the simulated ideal monitoring signal with errors such as detector noise, drifts, deviations in shutter delay times, etc. The values of these disturbances are specific to the deposition tool. They were determined based on the broadband spectra of actual coating runs. By starting a virtual coating run with defined disturbances, the thickness deviations expected with a selected strategy can be assessed and the development of thickness deviations during the run, i.e. error compensation and error accumulation can be simulated. Within the software, parameters for the termination of each layer can be varied individually and the effect on the coating result can be observed. In order to demonstrate the capability of this tool, a specific coating design was then selected. For this design various monitoring strategies were tested, broadband strategies with different wavelength ranges, monochromatic strategies varying wavelength assignment per layer but also mixed strategies of broadband and monochromatic monitoring. The most stable monitoring strategy resulting from these simulations was coated as well as some of the less promising candidates and their results were compared.
In this work we want to demonstrate how the methodology of Design of Experiment (DOE) can be used for the
development of ion-assisted ITO films deposited at low temperatures. The optimization method allows us to identify the
process parameters, which yield films with high transmittance and low resistivity. The article will show the results
obtained for transmittance and resistivity. Furthermore, the dispersion of the refractive index and the extinction
coefficient will be determined as well as the surface roughness. In ITO there is a trade-off between transmittance /
absorbance and sheet resistance. Virtually absorption free films could be obtained with a resistivity of 3.2 μΩm, whereas
the lowest resistivity (2.7 μΩm) yielded a transmittance, which was reduced by a few percent.
In this manuscript we present the development of an integrated shearography system that is able to measure the 3D deformation of an object surface. In order to determine all six displacement derivatives that may contribute to shearography results, six measurements with three different sensitivity directions and two shear directions have to be performed. The realized system is able to perform this measurement sequence in an automated way.
Electronic speckle pattern shearing interferometry (ESPSI) allows for the measurement of displacement derivative maps. To monitor the stress/strain state of an object surface and its material properties, it is necessary to measure more than one displacement derivative map. The conventional configuration of ESPSI has been modified by parallel adaptation of Michelson shearing interferometers and an optoelectronic/image processing head with the capability of simultaneous capturing of 2 images. The automatic analysis of speckle fields is performed by temporal phase stepping method with the separation of the information by orthogonal polarization states. In the paper the opto-mechanical and electronic configuration of the system is presented. The experimental results obtained in the modified ESPIS system, when applied to determination of shear strain in a tensile loaded aluminium specimen are also presented.
Recently, a method to remove the effect of the shear distance from shearographic recordings by reconstruction of the displacement field was presented. Conventional phase- shifting shearography is used to obtain a phase map which represents an approximation to the displacement derivative. To calculate the displacement information of r a point in the final image, the phase values of certain image points of the shearogram are added. Applying this summation top all image points results in a phase map representing the displacement field with the effect of image-doubling removed. This manuscript concentrates on the experimental verification of the effect and shows the application to the measurement of out-of-plane as well as in-plane deformation. The method combines the advantages of conventional shearography and electronic speckle pattern interferometry displacement measurement. It uses the same optical set-up as shearography, which has proved its applicability in industrial environments, and delivers the displacement field with the effect of image-doubling removed. This displacement field is easier to interpret than the approximated displacement derivative of conventional shearography.
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