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

Fensterbeschichtung mit Durchblick: In-situ-Kontrolle der optischen Behandlung von Architekturglas

Die Herstellung moderner optischer Dünnschichtsysteme erfolgt heute fast ausschließlich durch Vakuum-Beschichtungsverfahren. Erforderlich ist dazu eine Anlagentechnik, die sowohl die hohen Qualitätsanfoderungen an die Beschichtung erfüllt als auch ein effizientes Auftragen der Schichten ermöglicht. Zum Erreichen dieser Ziele ist die spektroskopische Ellipsometrie als zerstörungsfreies und empfindliches Verfahren gut geeignet. Dabei wird die Änderung des Polarisationszustandes von linear oder zirkular poalarisiertem Licht nach einer Reflexion von der Oberfläche spektral analysiert. Bisher gehört die spektroskopische Ellipsometrie nicht zum Stand der Technik im Einsatz bei industriellen Glasbeschichtungsanlagen. Im Rahmen eines vom BMBF geförderten Industrie-Verbundprojektes wurden ellipsometrische Untersuchungen in einer Inline-ex-Situ-Anordnung an einer Glasbeschichtungsanlage durchgeführt. In der Messanordnung kann das fertige Schichtsystem monitoriert werden. Um ellipsometrische Messungen im Produktionsprozess auf einer Inline-Anlage durchführen zu können, entwickelte Sentech Instruments, Berlin, einen neuen Messkopf. Dieses System kommt mit nur einem Vakuumflansch aus, was für Messungen an einer Inline-Anlage von entscheidendem Vorteil ist. Mit dem Gerät konnte das Schichtsystem Vakuum - Glas - SnO2 (30 nm) - ZnO (3 nm) - Ag (10 nm) -NiCrOx (5nm) - Vakuum monitoriert werden. Besondere Bedeutung wird das Messverfahren möglicherweise erlangen, wenn noch komplexere, zur Zeit in Entwicklung befindliche Schichtsysteme in die Produktion umgesetzt werden

Comparison of abrasive tests for transparent optical coatings

Many standardised abrasion tests are available but not all are appropriate for transparent coatings. Therefore we had a closer look at two methods in this study: we used the oscillating sand method and the sand trickling test for a series of different samples. The first one is like a hard grinding and the second one is an impact test. Also adequate techniques have to be applied for the determination of abrasion. We executed haze measurements as well as ellipsometry. The hardness and size of the test media influences the damage. Thus two types of test media were utilised: silica and corundum. The results of the abrasive tests are compared to the hardness of the coating materials

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

Recent developments in precision optical coatings prepared by cylindrical magnetron sputtering

Cylindrical targets give the opportunity to improve the process stability of magnetron sputtering processes although reactive deposition might be a challenge. Sputtering from metal doped oxide targets in connection with a plasma source unlocks the full potential: the process can be driven in well-known mid-frequency mode and the plasma source ensures fully stoichiometric films with low loss. During the last years different developments for oxide cylindrical targets were done. The suitable composition has to be found regarding e.g. the density and an arc-free process as familiar for planar targets. In the tube geometry new manufacturing methods are required that ensure these properties. In the present paper we show some examples of the high refractive index materials tantalum oxide: single film characterization as well as realized complex precision optical filters. The results are accompanied by performance measurements in terms of uniformity over 200 mm glass wavers as well as carrier to carrier and batch to batch. These were measured by the position of a quarter-wave stack's edge