Deposition and spectral performance of an inhomogeneous broadband wide-angular antireflective coating

The gradient index coatings and optical filters based on them are a challenge for fabrication. In a round-robin experiment basically the same hybrid antireflection coating for the visible spectral region has been deposited with three different techniques: electron beam evaporation, ion beam sputtering and radio frequency magnetron-sputtering. Spectral performances of such one-side and both-side coated samples have been compared with corresponding theoretical spectra of the designed profile. Also, reproducibility of each process is checked

Sauber durch die Sonne: Photokatalytische Schichten

Ein bisschen Sonnenlicht – und Oberflächen reinigen sich von selbst. In die Oberfläche eingebaute Titandioxidmoleküle setzen, aktiviert von UV-Licht, eine Reaktion in Gang, die Bakterien, Algen und Pilze zersetzt und beispielsweise die Armlehnen von Gartenstühlen sauber hält

Properties of TiO2 films deposited by bipolar reactive HiPIMS

TiO2 films are deposited with partial pressure controlled bipolar high power impulse magnetron sputtering (HiPIMS) sputtering. By the reduction and control of the oxygen partial pressure, the deposition rate could be increased by a factor of 3 compared to the oxide mode. A high index of refraction (n> 2.6 at 550 nm) formerly observed in transition mode at higher deposition rates. The high refractive index in also is agreement with XRD measurements, which shows a pronounced rutile phase. An increased absorption is also observed by optical analysis

Magnetron sputtering of precision optical coatings enabled by process stability of rotatable cathodes

Cylindrical rotatable cathodes deliver huge material amounts under stable conditions as needed for interference coatings. Sub-stoichiometric targets and plasma oxidation produce low absorbance and virtually no drift of refractive index associated with changeless material uniformity

Entwicklung eines hochintegrierten digitalen Hochleistungsbelichters für die Belichtung von Lötstopplacken (DAHLIA): Schlussbericht im Projekt; Laufzeit des Vorhabens: 01.12.2015 - 30.11.2018

As part of the subproject, the metrological prerequisite was initially created to be able to measure the filter to be produced at all. For this purpose, a spectrometer was designed and contructed with which the s- or p-polarized transmission con be measured at angles of incidence to be set. The coating process has been improved in terms of scattering and absorption losses. A significant improvement of the scattering losses was achieved by modified process parameters. Relevant in this context is also the roughness of the substrates, which goes directly into the optical losses. Best results were obtained with superpolished substrates (P4) with a roughness (5 x 5 µm) better than 0.2 nm. Through a suitable layer design and an adapted monitoring strategy, filters with a very steep edge could be produced successfully. The width is below the resolution of the spectrometer and the angular divergence of the measuring beam of the insitu spectrometer. Edge filters with different wavelengths within a batch could be realized by shifting the carriers. The change in the distance between the target and the substrate resulted in a rate change that could be used very precisely to adjust the central wavelength

Impact of thin film fabrication to the optimization process of a multispectral chromatic camera

A fabrication tolerant thin film design is presented. The optimization method is formulated in a six dimensional color space and stochastical variations during manufacturing are treated as an equivalent source of camera noise

Properties of cosputtered SiO2-Ta2O5-mixtures

In this work, different mixtures of SiO2 and Ta2O5 films were investigated for application in Rugate-filter-design. Not only optical properties were considered but also the mechanical and stoichiometric behavior especially with increasing thermal strain. It could be shown that different compositions of SiO2 und TA(2)O(5) show different behavior with increasing temperature. Furthermore, it was detected that the requirement of oxygen strongly correlates with the ratio of the two layer materials. Latter results in changes of the optical properties, which can entail the destruction of the optical performance of a Rugate filter. At the end of this article, some suggestions for Rugate design calculations are presented taking the results of this work into account

Deposition of abrasion resistant single films and antireflective coatings on sapphire

A series of different oxide and nitride antireflective coatings as well as single films on sapphire substrates have been deposited by magnetron sputtering. The layer stacks consist of 5–7 individual layers with a total thickness of around 300nm. Both high-index materials and low-index material were analyzed. The mechanical stability was investigated by means of optical haze increase during falling sand (“sand trickling test”) and by thickness loss during oscillating abrasionin a sand bath (tightened “Bayer test”). The dependence of the abrasion tests results on mechanical film properties, i.e. the nanoindentor hardness, was analyzed. No clear correlation of the Bayertest results and the sand trickling test results was found, which indicates that the abrasion mechanisms are different. A nitride basedantireflective coating with excellent properties from both tests has been produced