Iridium wire grid polarizer fabricated using atomic layer deposition

In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved

Optical Coatings with Atomic Precision

Atomic layer deposition allows for conformal coatings on arbitrarily shaped surfaces — and with nanopores, performance capabilities go even higher

Leistungsfähigere Entspiegelungen: Neue Technologien ermöglichen deutliche Fortschritte bei der Entspiegelung optischer Linsen

Optische Systeme aus mehreren Linsen sind heute ohne Entspiegelung der Oberflächen undenkbar, denn an jeder nicht entspiegelten Grenzfläche zur Luft würden mehrere Prozent des einfallenden Lichts durch Reflexion verloren gehen. Besonders auf dem Markt für Kameraobjektive werden hochwertige optische Linsen benötigt, deren gekrümmte Oberflächen bis in die Randbereiche gut entspiegelt sein müssen

Antireflection Coatings for Strongly Curved Glass Lenses by Atomic Layer Deposition

Antireflection (AR) coatings are indispensable in numerous optical applications and are increasingly demanded on highly curved optical components. In this work, optical thin films of SiO2, Al2O3, TiO2 and Ta2O5 were prepared by atomic layer deposition (ALD), which is based on self-limiting surface reactions leading to a uniform film thickness on arbitrarily shaped surfaces. Al2O3/TiO2/SiO2 and Al2O3/Ta2O5/SiO2 AR coatings were successfully applied in the 400-750 nm and 400-700 nm spectral range, respectively. Less than 0.6% reflectance with an average of 0.3% has been measured on a fused silica hemispherical (half-ball) lens with 4 mm diameter along the entire lens surface at 0 degrees angle of incidence. The reflectance on a large B270 aspherical lens with height of 25 mm and diameter of 50 mm decreased to less than 1% with an average reflectance < 0.3%. The results demonstrate that ALD is a promising technology for deposition of uniform optical layers on strongly curved lenses without complex in situ thickness monitoring

Controlling mechanical, structural, and optical properties of Al2O3 thin films deposited by plasma-enhanced atomic layer deposition with substrate biasing

Complex interference multilayer systems typically implemented in high-performance optics consists of several layers of low and high refractive index materials. Low mechanical stress of the coatings is desired to avoid cracking and delamination of the film or a deformation of the substrate. It is known that the ion energies in plasma-assisted deposition can be employed to control material properties and thereby mechanical stress. In this study, we evaluate the influence of substrate biasing on mechanical stress and optical properties of alumina (Al2O3) coatings deposited by plasma enhanced atomic layer deposition (PEALD). Substrate biasing up to -300 V was applied during O2 plasma exposure in the second step of a two-step PEALD process. To distinguish the physical effect of ion bombardment from the physico-chemical effect, a substrate bias of -100 V was applied separately and only during Ar plasma exposure that constituted the third step of a three-step PEALD process. Al2O3 films were characterized using spectroscopic ellipsometry, spectrophotometry, xray photoelectron spectroscopy (XPS), x-ray diffractometry (XRD), x-ray reflectometry (XRR), Fourier transform infrared spectroscopy (FT-IR), wafer-curvature measurement and atomic force microscopy (AFM)

The excited-state geometry of 1-hydroxy-2- acetonaphthone: a resonance Raman and quantum chemical study

1-Hydroxy-2-acetonaphthone (HAN), an intramolecular proton transfer system, was investigated in the present study by means of quantum chemical calculations and resonance Raman spectroscopy. To determine the Franck-Condon parameters, a time-dependent approach for the analysis of the resonance Raman spectra was applied. About 18 vibrational modes were found to be involved in the initial dynamics of HAN upon photo excitation. Moreover, the excited-state geometry of HAN was optimized at the CASSCF level of theory and the displacement parameters were determined. A very good agreement between the theoretical and experimentally derived parameters was obtained. The vibrations with the highest displacements correspond to stretching and in-plane deformation modes of the naphthalene ring and the conjugated carbonyl group, while the OH stretching mode exhibits no observable enhancement. Hence, a general molecular rearrangement takes place upon photo excitation, where the intramolecular oxygen-oxygen distance reduces corresponding to a redistribution of the electron density. Copyright ? 2006 John Wiley & Sons, Ltd.NRC publication: Ye

Light scattering characterization of single-layer nanoporous SiO2 antireflection coating in visible light

Antireflective coatings are widely applied on transparent optical components to reduce reflections at surfaces. Nanoporous silica (NP SiO2) thin films with tailored refractive index properties are used as single-layer antireflective coatings providing nearly zero reflectivity. In this work, light scattering properties of nanoporous silica single-layer antireflective coatings are investigated in order to determine their optical quality by means of total scattering and detailed roughness analysis. Scattering and roughness characterization of the samples coated with different film thicknesses were realized to distinguish the influences of nanopores and surface roughness on scattering losses in the visible (VIS) spectral range. No significant correlation of scattering losses with the film thickness is found, showing negligible influence of the nanopores to the overall scattering properties compared with the dominating effect of interface roughness. Moreover, the scattering losses from coated fused silica glass were observed as low as 20 ppm (0.002%). It is confirmed that NP SiO2 single-layer antireflective coatings are suitable to be used in optics demanding extremely low scattering characteristics

Laser-induced damage threshold of nanoporous single-layer ALD antireflective coatings

Atomic layer deposition (ALD) enables coating complex shaped substrates with excellent uniformity along the surface of the optic. Recently developed nanoporous SiO2 layers have been applied as single layer antireflection coatings on fused silica substrates at both 1064 nm and 532 nm wavelengths. The LIDT in the nanosecond regime at both 1064 nm and 532 nm of these nanoporous SiO2 coatings as well as the bare substrates were investigated. The stability of the coatings with respect to LIDT has been evaluated under normal atmospheric conditions, dry air with relative humidity < 10% and nitrogen atmosphere. The multiple pulse damage characteristic for 5000 shots showed in all cases no significant pulse dependence. At 532 nm wavelength, the 0%-LIDT value is between 60 J/cm 2 and 70 J/cm 2 , which is comparable to the values measured on uncoated substrates (80 J/cm 2 ). In case of 1064 nm the 0%-LIDT is only between 40 J/cm 2 and 50 J/cm2 (uncoated substrate: 100 J/cm 2 ) which is attributed to generated defects during the fabrication process