Hybrid optics for the visible produced by bulk casting of sol-gel glass using diamond-turned molds

Recent combinations of diffractive and refractive functions in the same optical component allow designers additional opportunities to make systems more compact and enhance performance. This paper describes a research program for fabricating hybrid refractive/diffractive components from diamond-turned molds using the bulk casting of sol-gel silica glass. The authors use the complementary dispersive nature of refractive and diffractive optics to render two-color correction in a single hybrid optical element. Since diamond turning has matured as a deterministic manufacturing technology, techniques previously suitable only in the infrared are now being applied to components used at visible wavelengths. Thus, the marriage of diamond turning and sol-gel processes offers a cost-effective method for producing highly customized and specialized optical components in high quality silica glass. With the sol-gel casting method of replication, diamond-turned mold costs can be shared over many pieces. Diamond turning takes advantage of all of the available degrees of freedom in a single hybrid optical element: aspheric surface to eliminate spherical aberration, kinoform surface for control of primary chromatic aberration, and the flexibility to place the kinoform on non-planar surfaces for maximum design flexibility. The authors discuss the critical issues involved in designing the hybrid element, single point diamond-turning the mold, and fabrication in glass using the sol-gel process

Synthesis And Linear And Nonlinear Photophysical Characterization Of Two Symmetrical Pyrene-Terminated Squaraine Derivatives

Two indole-based squaraine dyes, bearing two pyrenyl groups through vinyl or ethynyl linkers, were synthesized with the aim of enhancing the intramolecular charge transfer interaction in addition to improving their optical properties. The absorption and emission properties of these derivatives were determined to gain insight into the intensity of this type of interaction, their aggregation behavior, and for comparison with results obtained through quantum chemical calculations. Both compounds exhibited high photochemical stability, high molar absorptivity, large fluorescence quantum yields, and relatively low tendency of forming excimers in several solvents. Nonlinear spectroscopic studies revealed two-photon absorption (2PA) cross section maxima greater than 10 000 GM (1 GM = 1 × 10-50 cm4 s/photon), which are higher values relative to the indole-based squaraine core. Experimental results were compared with time-dependent DFT calculations. These observations contribute to the study of intramolecular charge transfer interaction, and its tailoring for the improvement of linear and nonlinear optical properties as well as suggests a paradigm in the construct of highly absorbing organic molecules containing pyrenyl groups for the development of new photonics materials

Sol-gel replicated optics made from single point diamond turned masters exhibit fractal surface roughness

Deterministic optics manufacturing, notably single point diamond turning (SPDT) has matured such that the current generation of machines is capable of producing refractive and reflective optics for the visible wavelength region that are quite acceptable for many applications. However, spiral tool marks are still produced that result in unwanted diffractive scattering from grating-like features having a spatial frequency determined by the machine feed, tool radius, and other influences such as vibration and material removal effects. Such regular artifacts are the characteristic of deterministic manufacturing methods such as SPDT. The authors present some initial findings suggesting that fractal, or non-deterministic surfaces can be produced by SPDT through sol-gel replication. The key is the large isotropic shrinkage that occurs through monolithic sol-gel replication (a factor of 2.5) that results in all features, including tooling marks, being reduced by that amount. The large shrinkage itself would be a laudable-enough feature of the replication process. However, by an as-yet-not understood manner, the replication process itself seems to alter the roughness character of the replicated surface such that it appears to be fractal when analyzed using contact profilometry and the power spectrum approach

Mechanism of Nonlinear Optical Enhancement and Supramolecular Isomerism in 1D Polymeric Zn(II) and Cd(II) Sulfates with Pyridine-4-aldoxime Ligands

Interaction of zinc(II) and cadmium(II) sulfates with pyridine-4-aldoxime (4-pyao) and pyridine-4-amidoxime (4-pyamo) ligands resulted in four 1D metal-organic materials (MOMs) with identical composition, [M(SO 4)A2(H2O)2]n, where M = Zn(II), A = 4-pyao for 1, M = Cd(II), A = 4-pyao for 2, M = Zn(II), A = 4-pyamo for 3, M = Cd(II), A = 4-pyamo for 4, and mononuclear [Zn(SO4)(4- pyamo)2(H2O)3] 5. New coordination polymers represent the mixed-ligand supramolecular isomers different by the twisting of two pyridine-4-oxime ligands in the metal coordination environments, and crystallizing in the different space groups. Conformational preferences and nonlinear optical properties of the 4-pyao and 4-pyamo complexes were investigated using density functional theory. Spectral properties of 1-3 have been also evaluated. The solid-state emission of 1D polymers 1-3 appears to be ligand-based, as the positions of the emission maxima remain practically unchanged from free ligand to complexes. The enhancement of luminescence and two-photon absorption in polymers in comparison with the pure ligands is attributed to the chelation of the ligand to the metal center. The detailed mechanism of this enhancement upon complex formation is analyzed and can be used in future design of metal-organic nonlinear optical materials. © 2014 American Chemical Society