Lanthanide borates, LnBO3, were prepared via hydrothermal methods, specifically supercritical basic water, in sizes up to 3 X 0.5 X 0.5 mm and their crystallographic, physical, and optical properties studied. The materials are thermally stable up to 1000 degrees C and their crystal structure, although previously thought to be centric orthorhombic, is shown to be orthorhombic yet acentric as is confirmed by the observance of second harmonic generated light. Absorption and luminescence from the NdBO3 and PrBO3 is provided and discussed, along with the corroboration that these materials have bandgaps well above 5 eV. This work marks these lanthanide borates as candidate materials for deep-UV and nonlinear optical applications.

The physical properties of single crystals are highly dependent on trace impurities contained within them. For synthesis of single crystals with prescribed properties, precise and accurate control of impurity content can be extremely desirable. We review and expand on studies of crystal from the natural environment that document systematic order-of-magnitude variations in defect abundances. Using high-resolution FTIR, we demonstrate that the dominant control on the uptake of defects in growing quartz crystals is the growth rate of the advancing crystal face. We show that the uptake of different kinds of defects have the same functional dependence both on crystal growth rate and on the crystallographic orientation of the growth face. In unaltered quartz crystals, concentrations of LiOH, HOH species and Al-bearing species are proportional to one another despite fast and slow growth on both 'r' and 'z' rhombohedral growth faces. In addition, our measurements can distinguish the effects of processes, such as internal diffusion and fluid exchange, which have re-set the abundances of defect specs after crystal growth; AlOH, HOH, and LiOH show increasing propensities for secondary mobility and are dependent on the crystallographic orientation of the original growth face which incorporated them.

The current report demonstrates the temperature vs. transmission vs. resistivity relationship for the less explored IR wavelength range of 6 to 22 micrometers for silicon and 10 to 22 micrometers for germanium over the temperature range of -100 degrees C to 25 degrees C. These studies involve a wide range of resistivities. Material samples include n- type Si of 4000, 160, and 12 ohm-cm, and n-type Ge of 35, 2.5, and 0.5 ohm-cm. Silicon has useable transmission bands only between 1.2 and 8.5 micrometers , between 14 and 15.6 micrometers , and greater than 20 micrometers with best transmission occurring between 1.2 and 6.5 micrometers . Germanium has a useable transmission band between 2 and 17 micrometers with best transmission between 2 and 11.5 micrometers . The temperature dependence of IR transmission becomes more pronounced with increasing wavelength: 1.5 percent to 11.5 percent and 3 percent to 9.5 percent for silicon and germanium respectively over the temperature range of -100 degrees C to 25 degrees C. The 4000 ohm-cm Si sample exhibits significantly greater transmission at wavelengths of both 9.0 and 19.5 microns. The temperature dependence of lattice absorption is observed in germanium. This study builds a bridge between previously determined absorption mechanisms of the near and far IR ranges and may be used to develop the feasibility of silicon and germanium as optical windows or lenses within an extraterrestrial environment.

Photoluminescence (PL) of pure and 0.2 mol percent Sm³⁺ doped zirconium oxide prepared by the Sol-Gel process and annealed at 1000 degrees C to stabilize the monoclinic phase were performed. The experimental spectra suggest the presence of energy transfer pro9cesses between the host and the dopant when the host was excited with a signal centered at 320 nm. The Sm³⁺ doped monoclinic zirconium oxide shows strong emission at the green and red bands, corresponding to the ⁴G_5/2 yields ⁶H_5/2 and ⁴G_5/2 yields ⁶H_7/2 samarium transition, respectively; whereas the undoped sample only shows a broad band emission centered at 495 nm. The main mechanism that allows the samarium emission under UV-excitation appears to be non-radiative energy transfer from the ZoO₂ host to the Sm³⁺ ions.

Spectroscopic properties of Nd³⁺ in barium fluoroborophosphate and barium fluorosulphatephosphate glassy matrices have been analyzed by fitting the experimental data with the standard Judd-Ofelt theory. Various spectroscopic parameters viz. Radiative transition probabilities, radiative decay time, stimulated emission cross sections and quantum efficiency of the principal fluorescence transition from the ⁴F_3/2 metastable level are obtained. Results show that addition of borate content to the fluorophosphate matrix will reduce the fluorescence spectral properties of Nd³⁺, whereas the influence of sulphate content is to improve the fluorescence spectral properties over a considerable extent. A comparison of the radiative properties of two hosts with that of fluorophosphate shows that the performance of the fluorosulphatephosphate matrix is superior and hence can be considered as possible candidate for solid state laser amplifiers.

High-efficiency Bragg gratings were created in sodium-zinc- aluminum-silicate glass doped with cerium, silver, and fluorine. Recording is a two-step process. The first step is a glass exposure to UV radiation. The second is a thermal development for crystalline phase precipitation in the exposed areas. The relative and absolute diffraction efficiency has been measured at different wavelengths for different doses of irradiation and conditions of thermal development. Refractive index changes in the volume of PTR glass have been measured by using interferometry techniques and by volume Bragg grating characterization. Absolute diffraction efficiency above 96 percent was observed. Spatial frequencies from a few hundred to ten thousand lines per millimeter were achieved. Gratings working both in transmitting and reflecting modes are demonstrated. High photosensitivity allows recording at exposures below 1 J/cm². PTR Bragg gratings are stable up to 400 degrees C. Novel volume holographic elements have been made from Bragg diffractive gratings in PTR glass including transmitting and reflecting volume diffractive elements. The use of such diffractive elements for laser and telecommunication are discussed.

Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.

With the number of cerium doped radiation resistant glasses available to the designer of space optics rapidly decreasing, it is critical to identify and characterize all potential sources of radiation resistant glasses and crystals. Unfortunately much of the data on radiation testing of glasses is quite old and often not completed at very high dose rates as might be experienced by an unshielded space optic in orbit for many years. In addition, many optical glasses and crystals are manufactured today with much higher purity than in the past in order to increase their ultraviolet transmission properties. Consequently these glasses are much more resistant to space radiation than in the past. In this paper we will present gamma radiation effects on the transmission properties of today's fused silica, sapphire, calcium fluoride, barium fluoride, Schott cerium doped radiation resistant glasses, Schott colored glass filters, as well as some infrared glasses with up to a 10 Mrad dose.

The results of fracture testing are usuaJly documented in terms of a measured strength, M ? where designates the arithmetic average of the recorded peak stresses at failure, and io represents the standard deviation. This "strength" '7M does not provide an objective measure of the intrinsic strength since M depends on the test method and the size of the volume or the surface subjected to tensile stresses. In this paper, we take advantage of Weibull's the- ory of fracture for providing an improved description of the failure statistics of sapphire test specimens subjected to biaxial stresses. For that purpose, we make use of the results of "ring-on-ring" flexural testing that was carried out over a period of 18 years at mechanical test facilities operated by the Southern Research Institute (SoRI), the University of Massachusetts (UMass), and the University of Dayton Research Institute (UDRI). Experiments were conducted, at room temperature, on test specimens supplied by two vendors and included mechanically polished as well as compressively coated specimens in the form of planar disks of different crystallographic orientation. Since equibiaxial flexure testing has now been adopted as the preferred method for assessing the strength of ceramics, we describe the failure probability in terms of a characteristic strength—i. e. , the effective strength for a 1-cm2 uniformly stressed area—, which allows one to evaluate the effective strength under different experimental conditions if the Weibuil modulus is available. The characteristic strengths (oc) and Weibull moduli (m) are predicated on a two-parameter model and validate the applicability of the area scaling law. Specifically, we conclude that: (a) The characteristic strength of polished c-plane sapphire is of the order of 975 MPa (140 kpsi) and the Weibull modulus is close to 3.4. (b) The strength of r-plane sapphire is substantially lower (oc 550 MPa 80 kpsi), but so is the scatter (m 4.1). And (c) strongly adhering compressive coatings can augment the strength by as much as 60 %,in accord with predictions based on simple fracture-mechanical considerations.

There is effect of nonlinear light propagation through dielectric with small non-absorbing micro inclusion that can play important role in initiating of laser-induced damage of transparent materials. The effect is developing of field instability in non-absorbing micro inclusions. It is shown that transparent micro inclusion can initiate local field increase accompanied by positive feedback resulting in further field increasing near the inclusion. If the electric field strength exceeds damage threshold during nonlinear evolution in the inclusion then developing of field instability results in damage of micro-inclusion before electric field reaches certain upper level determined by ionization processes. There is estimated threshold of field instability. Its dependence on material and radiation parameters is studied.

Transition metals are well known as optically active dopants in crystalline hosts because they fluoresce broadly in the near-IR; examples include Ti³⁺:sapphire (Al₂O₃) and Cr⁴⁺:forsterite (Mg₂SiO₄). Because transition element ions yield stronger optical activity with those of doped crystal. The glass-ceramic process can, in many cases, also allow the growth in glass of crystals which are difficult or impossible to obtain in single crystal form. Material properties and spectroscopic data are presented for transparent glass-ceramics based on transition element-doped forsterite, willemite, mixed Li-Zn-Mg- orthosilicates, and spinel crystals. The transition element ions include Cr⁴⁺ in tetrahedral coordination and Ni²⁺ in octahedral coordination. The optical property measurements of the transparent glass-ceramics, including absorbance, fluorescence, and fluorescence lifetimes, duplicate those reported in the literature for single crystal or powders. Cr⁴⁺- and Ni²⁺-doped glass-ceramics exhibit broad emission across the telecommunications wavelength range of 1100-1700 nm.

Detailed thermal expansion measurements and internal homogeneity measurements of the glass-ceramic material Zerodur were undertaken to examine its usefulness for EUVL. Repeat measurements on 100-mm long samples from three castings exhibit an expansion of approximately 12 +/- 2 ppb/K 2 (sigma) in the temperature range of interest for EUVL, corresponding to Class C of the draft SEMI 3148 standard. Internal homogeneity measurements reveal extremely small refractive index variations, suggesting comparably small compositional variations. This in turn is viewed as a necessary but not sufficient condition for high CTE uniformity, a factor required by EUVL applications.

A proprietary, inorganic, sol-gel joining technique was used to fabricate Zerodur-Zerodur-SiO₂ joints at temperatures 5000 psi, regardless of the heat treatment temperature from 25 to 120 degrees C. The strength of Zerodur-SiO₂ joints was 4500 psi. The Zerodur-Zerodur joints exhibited excellent dimensional stability perpendicular to the joint interface as there was no statistically significant difference between the coefficient of thermal expansion measured for joined and monolithic samples. The inorganic, sol-gel joining technique is an attractive technology that could be employed when fabricating light-weighted, dimensionally stable mirror blanks and microlithography stages.

The surface reactions of phosphate glasses are important for the processing and application of photonic devices, biomedical materials and conventional optical components. Of particular concern are the leaching of optically-active dopant species, surface layer formation and roughening during polishing, cleaning and other fabrication processes. In this study, the effects of various cleaning treatments, and both acid and base etching, were evaluated using surface analytical techniques (XPS, AFM). It is shown that in these phosphate glasses, the aluminum and rare-earth oxides have limited aqueous solubility, whereas the phosphate network is soluble over a wider range of pH. Thus, under those conditions where polishing damage can be removed by etching the surface, a localized precipitation of rare-earth oxides occurs which influences the final roughness and surface composition. Conversely, under conditions where this precipitation can be eliminated, an in-depth leaching of the surface occurs. These aqueous surface reactions were similar for both the optically-active and passive IOG-1 glasses. An optimized surface preparation method is described.

The use of magnesium aluminate spinel for optical windows, domes and armor has previously been investigated for a wide range of specific applications. The material properties rival that of ALON and sapphire, although there exists the potential for the fabrication of larger parts at significantly lower costs. The ability to fabricate transparent spinel by hot-pressing into large plates has gained interest for the fabrication of low-cost transparent armor for a range of applications. The present paper describes development efforts that are underway to fabricate spinel panels up to 22 inches in diameter and 0.5 inches thick. A 600 ton press is being installed at a facility in Millersville, MD that will be able to fabricate 22 inch diameter parts by late 2002. In the future, this press will potentially be able to fabricate 40 inch diameter plates with minimal changes. There is additional interest in these plates for large IR windows.