Thermally-induced nucleation and growth of secondary crystalline phases in a parent glass matrix results in the formation of a glass ceramic. Localized, spatial control of the number density and size of the crystal phases formed can yield ‘effective’ properties defined approximately by the local volume fraction of each phase present. With spatial control of crystal phase formation, the resulting optical nanocomposite exhibits gradients in physical properties including gradient refractive index (GRIN) profiles. Micro-structural changes quantified via Raman spectroscopy and X-ray diffraction have been correlated to calculated and measured refractive index modification verifying formation of an effective refractive index, neff, with the formation of nanocrystal phases created through thermal heat treatment in a multi-component chalcogenide glass. These findings have been used to define experimental laser irradiation conditions required to induce the conversion from glass to glass ceramic, verified using simulations to model the thermal profiles needed to substantiate the gradient in nanocrystal formation. Pre-nucleated glass underwent spatially varying nanocrystal growth using bandgap laser heating, where the laser beam’s thermal profile yielded a gradient in both resulting crystal phase formation and refractive index. The changes in the nanocomposite’s micro-Raman signature have been quantified and correlated to crystal phases formed, the material’s index change and the resulting GRIN profile. A flat, three-dimensional (3D) GRIN nanocomposite focusing element created through use of this approach, is demonstrated.

The physical properties of chalcogenide glasses in the (GeSe2-3As(2)Se(3))(1-x)PbSex (GAP-Se] series (x=0-55 mol%) have been measured as a function of PbSe content and glass morphology. Measurements of density, microhardness, thermal properties (glass transition, stability and conductivity) and IR transmission spectra have been correlated with Pb content illustrating the impact of liquid liquid phase separation (LLPS) on properties within this multicomponent chalcogenide glass system. The role of Pb as both a modifier and network participant is proposed as a structural interpretation of property variation across the series. Density, microhardness and thermal conductivity showed an increase with PbSe content whereas glass transition temperature (T-g) exhibits a minimum near the center of the immiscibility zone correlated to a decrease in glass stability when a Pb-rich matrix is present. The structural origin of the change in the properties is confirmed using Raman spectroscopy and transmission electron microscopy (TEM) which illustrate the different morphology of phase separation present and how it impacts property evolution.

PTR glass is a photosensitive silicate glass which imparts refractive index change after UV-exposure and thermal development. The origin of photosensitivity is explained by the precipitation of NaF crystals inside the glass matrix. While nucleation of NaF in PTR glass has been thoroughly studied, the mechanisms of growth of NaF crystals have drawn a limited interest. To study the NaF growth, several techniques were combined: optical spectroscopy, interferometry, DSC and XRD. It was found that the size of NaF crystals in UV-exposed PTR glass, as determined by the broadening of the diffraction lines does not exceed ~20nm. The NaF crystals' growth is limited by the exhaustion of Na+F− within the glass matrix as well as the increase of the viscosity of the glass surrounding the crystals that act as a kinetics barrier for further growth. X-ray diffraction analysis of NaF powder allowed calculating the crystals' volume fraction and their average size. A combination of these parameters with Rayleigh scattering model allowed the prediction of scattering at any wavelength and any thermal treatment, proving that scattering is determined by single crystals.

Next generation optical components will require materials that possess unique, spectral-specific optical function and forming-compatible attributes defined by their chemistry, structure and properties. Trade-offs in the optimization of these variables for manufacturability are discussed.

Mechanisms of photo-thermo-induced refractive index change, advances in glass properties and applications for holographic optical elements (volume Bragg gratings), laser beam profilers (volume diffusers), volume phase masks, and monolithic solid state lasers are discussed.

Photo-thermo-refractive (PTR) glass is a photosensitive multicomponent silicate glass that imparts refractive index change after exposure to ionizing radiation and thermal treatment. The origin of this photosensitivity is explained by thermal precipitation of sodium fluoride crystals controlled by atomic silver nucleation centers. These centers are produced by photo-reduction of silver ions resulted from photoionization (photo-oxidizing) of cerium ions. This feature of PTR glass is successfully used for high efficiency phase hologram recording. However, the mechanism of electric charge exchange (transfer) between these ions is not known and the role of intrinsic electron and hole centers was not studied. To elucidate this problem, pure PTR glass matrix with no dopants was prepared and the subsequent absorption spectra of color centers were studied after excitation of the intrinsic absorption edge of glass matrix. Color centers were bleached by thermal treatment and by optical excitation of induced absorption bands. The analysis of the structure of absorption spectra at different stages of coloration and bleaching led to the deconvolution of complex spectra to Gaussian components. Based on this analysis and comparison with simple silicate glasses, induced absorption bands were assigned to different intrinsic electron and hole centers. Interconversion of different centers is also studied.

Zeta potential measurements, optical microscopy and viscometry have been used to probe the behavior and the modified response to electrochemical and magnetic stimuli of cabonyl iron with other species present in the magnetorheological finishing fluid.