Levinebarnett6123

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.The wavefront error (WE) of a surface with an optical coating ("filter") is ideally measured at the in-band wavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-of-band wavelength (typically 633 nm), assuming that the filter transmits (for transmitted WE, or TWE) or reflects (for reflected WE, or RWE) at this wavelength. This out-of-band TWE/RWE is generally assumed to provide a good estimation of the desired in-band TWE/RWE. It will be shown in this paper that this is not the case for a large class of filters (i.e., bandpass) where the group delay is significantly different at the in-band and out-of-band wavelengths and where the optical filter exhibits a thickness non-uniformity across the surface. A theoretical explanation will be given along with an approach to predict the in-band TWE/RWE based on the coating non-uniformity, the measured out-of-band TWE/RWE, and the theoretical properties of the optical filter at the in-band and out-of-band wavelengths. A reasonable agreement between theory and measurement was demonstrated by measuring the TWE of an 11 nm wide bandpass filter (centered at 1048 nm) at both in-band (λ=1048nm) and out-of-band (λ=625nm) wavelengths. A similar treatment is provided for RWE.A comparative study was performed to investigate how etching methods and parameters affect the properties of SiO2 and HfO2 coatings. SiO2 and HfO2 single layers were prepared by electron-beam evaporation (EBE), ion-beam assisted deposition (IAD), and ion-beam sputtering (IBS). Then, ion-beam etching (IBE), reactive ion etching (RIE), and inductively coupled plasma etching (ICPE) were used to study the influence of ion bombardment energy and chemical reaction on the etching rates and properties of the prepared SiO2 and HfO2 single layers. For SiO2 coatings, chemical reaction plays a dominant role in determining the etching rates, so ICPE that has the strongest CHF3 plasma shows the highest etching rate. Moreover, all three etching methods have barely any influence on the properties of SiO2 coatings. For HfO2 coatings, the etching rates are more dependent on the ion bombardment energy, although the chemical reaction using CHF3 plasma also helps to increase the etching rates to some extent. JPH203 supplier To our surprise, the ion bombardment with energy as high as 900 V does not change the amorphous microstructure or crystalline states of prepared HfO2 coatings. However, the high-energy ion bombardment in IBE significantly increases the absorption of the HfO2 coatings prepared by all deposition techniques and decreases their laser damage resistance to different extents.Metal-dielectric phase-shifting multilayer optical elements have been developed, providing broadband, virtually dispersion-free polarization manipulation down to the few-cycle level. These optical elements are Ag/Al2O3 mirrors that operate in the spectral range from 500 to 100 nm, exhibiting reflectance higher than 95%, and a differential phase shift between the s- and p-polarization of about 90° distributed over four bounces. The mirrors have been designed, produced, and reliably characterized based on spectral photometric and ellipsometric data using a non-parametric approach as well as a multi-oscillator model. The optical elements were implemented into a few-cycle laser system, where they transformed linearly polarized few-cycle light pulses to circular polarization.Thin-film interference filters can be illuminated by a circular aperture at different angles. Each situation produces a different transmittance spectrum. We present an analytical model that, for small tilt angles, predicts the change in transmittance for an arbitrary position of the filter in three-dimensional space. The model is extended to take into account higher-order harmonics. We also derive a formula to predict the change in central wavelength, and we validate our results by comparison with thin-film transfer-matrix calculations. A key property of our approach is that the model can be combined with empirical data to predict the transmittance without knowing the filter design.Residual stress birefringence of highly reflective mirrors is a challenging problem due to its dubious origin and intricate nature. In this paper, the birefringences of highly reflective mirrors manufactured under the same deposition parameters but structured with different numbers of high- and low-refractive-index (HL) layer pairs are measured with the cavity ring-down technique by the mirror rotation method together with a differential loss approximation model. Experimental results show that birefringence retardation increases with the increasing number of HL layer pairs. Further measurements across the mirror surface indicate a non-uniform birefringence distribution, while curvature analysis of the stress-deformed surface provides more clues to the origins of birefringence.A framework to quantitatively calculate substrate bending after coating has been proposed. By introducing fitting parameters to modified Stoney's formula, the amount of bending has been calculated to accuracies of less than λ/10 at 633 nm for ion-beam sputtering and ion-beam assisted deposition processes.