Toward the fabrication of a 5-μm-resolution Wolter microscope for the National Ignition Facility (invited).

Advancements in computer-controlled polishing, metrology, and replication have led to an x-ray mirror fabrication process that is capable of producing high-resolution Wolter microscopes. We present the fabrication and test of a nickel-cobalt replicated full-shell x-ray mirror that was electroformed from a finely figured and polished mandrel. This mandrel was designed for an 8-m source-to-detector-distance microscope, with 10× magnification, and was optimized to reduce shell distortions that occur within 20 mm of the shell ends.

Modeling the hydrodynamic impact on the tool influence function during hemispherical subaperture optical polishing.

To fabricate high-precision and accurate optics relative to the optical design surface, a high level of deterministic control of material removal (i.e., the tool influence function, TIF) during subaperture tool polishing is required.

Additive Manufacturing of Optical Quality Germania-Silica Glasses.

Direct ink writing (DIW) three-dimensional (3D) printing provides a revolutionary approach to fabricating components with gradients in material properties. Herein, we report a method for generating colloidal germania feedstock and germania-silica inks for the production of optical quality germania-silica (GeO-SiO) glasses by DIW, making available a new material composition for the development of multimaterial and functionally graded optical quality glasses and ceramics by additive manufacturing. Colloidal germania and silica particles are prepared by a base-catalyzed sol-gel method and converted to printable shear-thinning suspensions with desired viscoelastic properties for DIW.

Towards predicting removal rate and surface roughness during grinding of optical materials.

A series of controlled grinding experiments, utilizing loose or fixed abrasives of either alumina or diamond at various particle sizes, were performed on a wide range of optical workpiece materials [single crystals of (sapphire), SiC, (YAG), , and (LBO); a --- glass ceramic (Zerodur); and glasses of : (ULE), (fused silica), and --- (phosphate)]. The material removal rate, surface roughness, and morphology of surface fractures were measured. Separately, Vickers indentation was performed on the workpieces, and the depths of various crack types as a function of applied load was measured.

3D-Printed Transparent Glass.

Silica inks are developed, which may be 3D printed and thermally processed to produce optically transparent glass structures with sub-millimeter features in forms ranging from scaffolds to monoliths. The inks are composed of silica powder suspended in a liquid and are printed using direct ink writing. The printed structures are then dried and sintered at temperatures well below the silica melting point to form amorphous, solid, transparent glass structures.

Fabrication of Large-area Free-standing Ultrathin Polymer Films.

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters.

Origins of optical absorption characteristics of Cu(2+) complexes in aqueous solutions.

Many transition metal complexes exhibit infrared or visible optical absorption arising from d-d transitions that are the key to functionality in technological applications and biological processes. The observed spectral characteristics of the absorption spectra depend on several underlying physical parameters whose relative contributions are still not fully understood. Although conventional arguments based on ligand-field theory can be invoked to rationalize the peak absorption energy, they cannot describe the detailed features of the observed spectral profile such as the spectral width and shape, or unexpected correlations between the oscillator strength and absorption peak position.

Estimation of excited-state absorption and photobleaching in Fe²⁺-doped lithium sodium silicate glass under exposure to high-power nanosecond laser pulses.

Fe-doped lithium sodium silicate glasses codoped with Sn and C to promote the Fe²⁺ redox state are investigated under simultaneous excitation at the first and third harmonics of a nanosecond Nd:YAG laser. The aim is to evaluate critical parameters associated with the potential use of this material as an optical filter that transmits the third harmonic but blocks the fundamental frequency. Estimations of the excited-state absorption coefficient and photobleaching (reduction of absorption at the fundamental) are provided.

Convergent polishing: a simple, rapid, full aperture polishing process of high quality optical flats & spheres.

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial shape (i.e., surface figure), will converge to final surface figure with excellent surface quality under a fixed, unchanging set of polishing parameters in a single polishing iteration.

Dynamics of defects in Ce³⁺ doped silica affecting its performance as protective filter in ultraviolet high-power lasers.

We investigate defects forming in Ce³⁺-doped fused silica samples following exposure to nanosecond ultraviolet laser pulses and their relaxation as a function of time and exposure to low intensity light at different wavelengths. A subset of these defects are responsible for inducing absorption in the visible and near infrared spectral range, which is of critical importance for the use of this material as ultraviolet light absorbing filter in high power laser systems. The dependence of the induced absorption as a function of laser fluence and methods to most efficiently mitigate this effect are presented.

Enhanced delamination of ultrathin free-standing polymer films via self-limiting surface modification.

Free-standing polymer thin films are typically fabricated using a sacrificial underlayer (between the film and its deposition substrate) or overlayer (on top of the film to assist peeling) in order to facilitate removal of the thin film from its deposition substrate. We show the direct delamination of extraordinarily thin (as thin as 8 nm) films of poly(vinyl formal) (PVF), polystyrene, and poly(methyl methacrylate). Large (up to 13 cm diameter) films of PVF could be captured on wire supports to produce free-standing films.

Optimized pitch button blocking for polishing high-aspect-ratio optics.

Pitch button blocking (PBB), involving attaching small pitch buttons between the back of a thin workpiece (i.e., optic) and a blocking plate, enables noncompliant convergent polishing in which the workpiece stiffness and block interface strength are maintained.