Courtney Kucera

Color kinetic nanoparticles.

Eu3+ doped LaF3 nanoparticles functionalized with a 3-4 formylphenyl benzoic acid ligand were synthesized. Excitation energy-dependent energy transfer from the ligand to Eu3+ yields color tunability from the red to greenish-blue as a function of excitation wavelengths. This synthetic approach provides large shifts in the resultant chromaticity with an excitation wavelength including the generation of white light.

Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles

This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF3:RE and PbF2, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF3/LaF3, and CaF2/CaF2 core/(multi-)shell nanoparticles, and the CaF2-LaF3 system.

Fluoride nanoscintillators

A preliminary investigation of the scintillation response of rare earth-doped fluoride nanoparticles is reported. Nanoparticles of CaF2 : Eu, BaF2 : Ce, and LaF3 : Eu were produced by precipitation methods using ammonium di-n-octadecyldithiophosphate (ADDP) as a ligand that controls growth and lessens agglomeration. The structure and morphology were characterized by means of X-ray diffraction and transmission electron microscopy, while the scintillation properties of the nanoparticles were determined by means of X-ray and 241 Am irradiation. The unique aspect of scintillation of nanoparticles is related to the migration of carriers in the nanoscintillator. Our results showed that even nanoparticles as small as ∼4nm in size effectively scintillate, despite the diffusion length of e-h pairs being considerably larger than the nanoparticles themselves, and suggest that nanoparticles can be used for radiation detection.

Spinel-derived single mode optical fiber

A silica-based highly acoustically-anti-guiding optical fiber, fabricated using a molten core approach employing spinel (MgAl2O4) for the first time, is presented. To our knowledge, this is the first truly single mode optical fiber fabricated from a precursor crystal. It is shown that MgO increases the acoustic velocity when added to silica (some physical parameters of MgO are identified) and that the Brillouin gain in the core is less than one third that in the cladding in one of the fibers. This results from a massive acoustic waveguide attenuation term that broadens the spectrum to well over 200 MHz. For the first time, to the best of our knowledge, this also enabled the validation of the intrinsic Brillouin line-width (~20 MHz) of pure silica in fiber form via a direct measurement.

Brillouin scattering properties of lanthano–aluminosilicate optical fiber

Utilizing measurements on a lanthano-aluminosilicate core optical fiber, the specific effects of lanthana (La2O3) on the Brillouin characteristics of silica-based oxide glass optical fibers are described. Lanthana is an interesting species to investigate since it possesses a wide transparency window covering the common fiber laser and telecom system wavelengths. As might be expected, it is found that the properties of lanthana are very similar to those of ytterbia (Yb2O3), namely, low acoustic velocity, wide Brillouin spectral width, and a negative photoelastic constant, with the latter two properties affording significant reductions to the Brillouin gain coefficient. However, lanthana possesses thermo-acoustic and strain-acoustic coefficients (acoustic velocity versus temperature or strain, TAC and SAC, respectively) with signs that are opposed to those of ytterbia. The lanthano-aluminosilicate (SAL) fiber utilized in this study is Brillouin-athermal (no dependence of the Brillouin frequency on temperature), but not atensic (is dependent upon the strain), which is believed to be, to the best of our knowledge, the first demonstration of such a glass fiber utilizing a compositional engineering approach.

Designer emission spectra through tailored energy transfer in nanoparticle-doped silica preforms

This Letter provides a qualitative proof of concept for purposefully tailoring the emission spectrum of glass by spatially localizing dissimilar dopants to control the degree of energy transfer. More specifically, modified-chemical-vapor-deposition-derived silica preforms were solution doped with either a solution of individually Eu(3+)- or Tb(3+)-doped nanoparticles or a solution of Eu(3+)/Tb(3+)-codoped nanoparticles. The preform prepared using the codoped nanoparticles exhibited energy transfer from the Tb(3+) to the Eu(3+) ions, whereas the preform containing individually doped nanoparticles yielded only discretely Tb(3+) or Eu(3+) emissions. The extension of this work to broadband amplifiers and lasers is discussed.

Brillouin Properties of a Novel Strontium Aluminosilicate Glass Optical Fiber

Presented here are the selected optical, physical, and Brillouin-related properties of a novel silica-clad, strontium aluminosilicate (SrAlSi) glass optical fiber produced using the molten core method. The Brillouin gain coefficient was found to be 0.11 × 10-11 m/W, which is about 20 × lower than conventional silica glass optical fibers. The SrAlSi core fiber also has a near-zero temperature coefficient of Brillouin frequency shift (-0.064 MHz/K) and can be considered athermal for all intents and purposes. Additional physical and Brillouin properties of the individual glass components are deduced through the use of an additive model. As a highlight, strontia (SrO) is found to have a large negative Pockels photoelastic coefficient of p12 = - 0.245. Various other bulk properties, such as the acoustic velocity, refractive index, mass density, thermo-optic, and thermo-acoustic, as well as strain-optic and strain-acoustic coefficients are provided.

Single- and few-moded lithium aluminosilicate optical fiber for athermal Brillouin strain sensing.

Results are presented toward realizing a true single-mode fiber whose Brillouin frequency shift is independent of temperature, while its dependence on strain is comparable to conventional high-silica-content single-mode fibers. Demonstrated here is a fiber with a negative thermal sensitivity dν/dT of -0.26  MHz/K and a strain sensitivity of +406  MHz/%. The suppression of the Brillouin thermal response is enabled by the large thermal expansion coefficient of the group I oxide-containing silica glass network.

Stability of Grafted Polymer Nanoscale Films toward Gamma Irradiation

The present article focuses on the influence of gamma irradiation on nanoscale polymer grafted films and explores avenues for improvements in their stability toward the ionizing radiation. In terms of applications, we concentrate on enrichment polymer layers (EPLs), which are polymer thin films employed in sensor devices for the detection of chemical and biological substances. Specifically, we have studied the influence of gamma irradiation on nanoscale poly(glycidyl methacrylate) (PGMA) grafted EPL films. First, it was determined that a significant level of cross-linking was caused by irradiation in pure PGMA films. The cross-linking is accompanied by the formation of conjugated ester, carbon double bonds, hydroxyl groups, ketone carbonyls, and the elimination of epoxy groups as determined by FTIR. Polystyrene, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, dimethylphenylsilanol, BaF2, and gold nanoparticles were incorporated into the films and were found to mitigate different aspects of the radiation damage.

Spectral engineering of LaF3:Ce3+ nanoparticles: The role of Ce3+ in surface sites

Due to the high surface-to-volume ratio, luminescence centers on the surface have relative dominance in the overall spectral response of nanoparticles. The luminescence of LaF3:Ce3+ nanoparticles was investigated in the spectral and temporal domains with a particular focus on the role of Ce3+ on the surface. These nanoparticles present two luminescence bands at 4.10 eV and 4.37 eV attributed to Ce3+ transitions from the 5d level to the spin-orbit split 4f ground levels 2F5/2 and 2F7/2, in addition to a low-energy band at 3.62 eV that has been attributed to Ce3+ ions residing in perturbed sites. The growth of up to three undoped shells, ca. 0.9 nm thick each, around the core promoted a progressive enhancement of luminescence output, concomitant with an increase in the fluorescence lifetime due to the weakening of energy transfer through multipolar interaction between Ce3+ in the core and quenching defects on the surface. Also, the growth of the first shell led to a decrease in the relative intensity of the...