convergent-polishing-simple-rapid-full-aperture-polishing-process

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats &amp; 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 ...

fabrication-of-large-area-free-standing-ultrathin-polymer-films

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 ...

Lawrence Livermore National Laboratory

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Characterization of proton exchange layer profiles in KD2PO4 crystals by micro-Raman spectroscopy.

Caract&eacute;risation des profils de couche de proton exchange dans les cristaux de KD2PO4 par spectroscopie micro-Raman.

Charakterisierung von Protonen-Austausch-Schicht-Profile in KD2PO4 Kristalle durch Mikro-Raman-Spektroskopie.

Caratterizzazione dei profili di strato proton exchange in cristalli KD2PO4 di spettroscopia micro-Raman.

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Caracterizaci&oacute;n de perfiles de capa de intercambio de protones en cristales de KD2PO4 por espectroscopia de micro-Raman.

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. This process has been optimized, and practical design criteria (number, size, and spacing of pitch buttons) have been determined both experimentally and theoretically using a thermoelastic model. The optimized PBB process has been successfully implemented on 100-265 mm sized workpieces with aspect ratios up to 45, resulting in maximum peak-to-valley heights of <|0.1| μm after blocking and polishing.

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

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. By modifying the substrate to lower the interfacial energy resisting film-substrate separation, the conditions for spontaneous delamination are satisfied even for very thin films. The substrate modification is based on the electrostatic adsorption of a cationic polyelectrolyte. Eliminating the use of sacrificial materials and instead relying on naturally self-limiting adsorption makes this method suitable for large areas. We have observed delamination of films with aspect ratios (ratio of lateral dimension between supports to thickness) of 10(7) and have captured dry, free-standing films with aspect ratios >10(6). Films with an aspect ratio of 10(5) can bear loads up to 10(6) times the mass of the film itself. The presence of the adsorbed layer can be observed using X-ray photoelectron spectroscopy, and this layer is persistent through multiple uses. In the system studied, elimination of sacrificial materials leads to an enhancement in the failure strength of the free-standing thin film. The robustness, persistence, and the self-optimizing nature distinguish this method from various fabrication methods utilizing sacrificial materials and make it a potentially scalable process for the fabrication of ultrathin free-standing or transferrable films for filtration, MEMS, or tissue engineering applications.

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

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. Experiments simulating the operation of the material as a UV protection filter for high power laser systems were performed in order to determine limitations and practical operational conditions.

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

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. The results provide insight on the design and expected operational parameters of this type of Fe-doped materials.

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

ArticleTotal : 2	Year
Publication title Cited by 11	2014
Publication title Cited by 10	2015

Article	Year
Characterization of proton exchange layer profiles in KD2PO4 crystals by micro-Raman spectroscopy. Applied spectroscopy\| PubMed ID: 15035718	2004
Optimized pitch button blocking for polishing high-aspect-ratio optics. Applied optics\| PubMed ID: 23262529	2012
Enhanced delamination of ultrathin free-standing polymer films via self-limiting surface modification. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 24784173	2014
Dynamics of defects in Ce<sup>3+</sup> doped silica affecting its performance as protective filter in ultraviolet high-power lasers. Optics express\| PubMed ID: 25402119	2014
Estimation of excited-state absorption and photobleaching in Fe<sup>2+</sup>-doped lithium sodium silicate glass under exposure to high-power nanosecond laser pulses. Applied optics\| PubMed ID: 25967187	2015

Tayyab Suratwala

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