Glass materials based on rare earth oxides and aluminum oxide can provide a combination of infrared transparency, strength, hardness, and environmental stability in a formable material. This article describes a new family of rare earth oxide-aluminum oxide glass materials that can be made by casting from melts formed in platinum crucibles. The glasses transmit light in the wavelength range from 0.3 to 5 μm in sections of ~0.3 cm, they have a Vickers hardness of 800-1000, and exhibit excellent environmental stability typical of refractory oxide materials. The composition of the glass can be adjusted to achieve refractive indices in the range 1.7-1.8 and Abbe numbers of 30-60. The materials are promising candidates for passive optical elements or as a host for optically active ions such as Yb or Nd that provide laser action or absorb at laser line wavelengths.
X-ray storage phosphors have several advantages over traditional films as well as digital X-ray detectors based on thin-film transistors (TFT). Commercially used storage phosphors do not have high resolution due to light scattering from powder grains. To solve this problem, we have developed storage phosphor plates based on modified fluorozirconate (ZBLAN) glasses. The newly developed imaging plates are “grainless” and, therefore, can significantly reduce light scattering and improve image resolution. To study the structure and image performance of the novel storage phosphor plates, we conducted X-ray diffraction (XRD) and X-ray imaging analyses at the Advanced Photon Source, Argonne National Laboratory. The XRD results show that BaCl<sub>2</sub> crystallites are embedded in the glass matrix. These crystallites enlarge and are under residual stress after heat treatment. The X-ray imaging study shows that these storage phosphor plates have a much better resolution than a commercially used storage phosphor screen. The results also show that some of the glass ceramics are high-resolution scintillators. Our study demonstrates that these fluorozirconate-based glass ceramics are a promising candidate for high-resolution digital X-ray detectors for both medical and scientific research purposes.
Glass and glass fibers formed from rare earth (RE) oxide-aluminum oxide compositions (REAlTM glasses) have properties similar to sapphire. They exhibit infrared transmission to wavelengths ~ 5000 nm; are hard and strong, thermally stable to ~ 1000°C, highly resistant to attack by aqueous solutions; and can be made into homogeneous products that contain large concentrations of optically active dopants. This paper describes the synthesis, optical properties, fluorescence lifetime measurements of Er<sup>3+</sup>- and Ho<sup>3+</sup>-doped glasses, and in-progress resaerch on materials that emit in the 2000-3000 nm wavelength range of interest for medical device applications. Effects of host glass compsition and dopant concentrations up to 32 mole% are presented.
Glasses based on rare earth oxide-aluminum oxide and containing high concentrations of Er<sub>2</sub>O<sub>3</sub>, Tm<sub>2</sub>O<sub>3</sub>, Yb<sub>2</sub>O<sub>3</sub>, or Ho<sub>2</sub>O<sub>3</sub> were synthesized. The host glass is strong, hard, highly resistant to chemical attack, and stable to temperatures ~1000°C. Addition of up to 20 mole % silica markedly increased glass formability while maintaining infrared transmission to ~ 5000 nm in sections up to a few mm. The fluorescence lifetime of excited states in the dopant ions was measured as a function of dopant concentration, pump power and host composition. The absorption cross section and fluorescence line shape were measured for selected compositions. We present details of the glass synthesis and properties, and results of the optical measurements in the context of developing glass-based optical devices.
The Moderate Resolution Imaging Spectrometer-Nadir (MODIS-N) for the Earth Observing System (EOS) is intended to provide daily global surveys for the atmosphere, the oceans, and the land. To achieve this capability, MODIS-N requires an at-least 2300-km swath width, and provides geometric-instantaneous-fields-of-view (GIFOVs) that are either 856 m, 428 m, or 214 m in size with reference to a 705 km satellite altitude. The 214 m GIFOV may or may not be used depending on total data rate impact assessments traded with science needs. To achieve the data for the multiplicity of science investigations MODIS-N provides nominally 36 spectral bands that are selected for specific locations and bandpasses in the spectral range from the visible to the long wave infrared. Another driver of this instrument combination is the need for long term spectral and radiometric calibration stability. Specific calibration capabilities are to be built into MODIS-N to achieve calibration knowledge over a 5 year operational life.