Showing papers by "Michael Bass published in 2008"

Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser

Abstract: Single mode laser action in a diode-pumped gain-guided, index- antiguided Nd3+-doped phosphate glass fiber having a 200-μm-diameter core is demonstrated. Near-Gaussian beam quality was maintained, even when pumped up to four times the threshold pump power, indicating robust lowest order mode oscillation. Subtle differences associated with the effectiveness of diode pumping gain-guided, index-antiguided fibers are discussed.

Sources of variation in baseline gene expression levels from toxicogenomics study control animals across multiple laboratories

Abstract: The use of gene expression profiling in both clinical and laboratory settings would be enhanced by better characterization of variance due to individual, environmental, and technical factors. Meta-analysis of microarray data from untreated or vehicle-treated animals within the control arm of toxicogenomics studies could yield useful information on baseline fluctuations in gene expression, although control animal data has not been available on a scale and in a form best served for data-mining. A dataset of control animal microarray expression data was assembled by a working group of the Health and Environmental Sciences Institute's Technical Committee on the Application of Genomics in Mechanism Based Risk Assessment in order to provide a public resource for assessments of variability in baseline gene expression. Data from over 500 Affymetrix microarrays from control rat liver and kidney were collected from 16 different institutions. Thirty-five biological and technical factors were obtained for each animal, describing a wide range of study characteristics, and a subset were evaluated in detail for their contribution to total variability using multivariate statistical and graphical techniques. The study factors that emerged as key sources of variability included gender, organ section, strain, and fasting state. These and other study factors were identified as key descriptors that should be included in the minimal information about a toxicogenomics study needed for interpretation of results by an independent source. Genes that are the most and least variable, gender-selective, or altered by fasting were also identified and functionally categorized. Better characterization of gene expression variability in control animals will aid in the design of toxicogenomics studies and in the interpretation of their results.

Temperature-dependent spectroscopic properties of Tm3+ in germanate, silica, and phosphate glasses: A comparative study

Abstract: Spectroscopic properties of thulium-doped germanate, silica, and phosphate glasses were measured and compared since such glasses are of interest as materials for fiber lasers in the eye-safe wavelength region. F43 excited state fluorescence decay dynamics was investigated at temperatures from 8to300K and the results revealed a strong dependence of the F43 lifetime on the host matrix. The temperature-dependent stimulated emission cross section was obtained by using the Fuchtbauer–Ladenburg technique. In phosphate glass the fluorescent lifetime is short, making this material difficult to use for 2μm laser purposes. Tm3+-doped germanate glass shows a longer lifetime than silica, a comparable value of stimulated emission cross section and some interesting temperature-independent properties.

Combination of up-converting materials with semiconductor light sources

Abstract: Methods, apparatus and systems for an up-converter resonant cavity light emitting diode device includes a semiconductor light source, an up-converter to form the light emitter with up-converting materials and an electrical source coupled with the semiconductor light source for providing electrical energy to the semiconductor light source to provide a desired wavelength emitted light. The semiconductor light source is a resonant cavity light emitting diode or laser that emits an approximately 975 nm wavelength to provide electrical and optical confinement to the semiconductor light source to form an up-converting resonant cavity light emitting diode (UC/RCLED). Rows and columns of electrodes provide active matrix addressing of plural sets of UC/RCLEDs for display devices. The up-converter resonant cavity light emitting diode device has applications in head mounted projection display optical system using spectrally selective beam splitters to eliminate spectral overlap between colors and to combine the red, green and blue beams.

Luminescence of Long-Term Ordered Pure and Doped Gallium Phosphide

Abstract: Evolution of luminescence is reported from GaP crystals that were grown over 40 years ago. This is the longest running cycle of experiments to study the temporal effects of crystal lattice and impurity ordering. The results clearly indicate impurity ordering and the formation of a new type of crystal lattice in which periodically disposed impurities modify and improve properties of the crystal. A high-density exciton system bound to a nitrogen impurity superlattice and GaP:N, GaP:N:Sm nanocrystals distributed in transparent fluorine-containing polymers will be used as the base elements for a new generation of optoelectronic devices.

Extending the tunability and spectral narrowing of Ti:Sapphire oscillator via Volume Bragg Grating based feedback

Abstract: A Ti:sapphire oscillator tunable over 138 nm and maintaining a spectral linewidth less than 15 pm with no spectral jitter is presented. Outputs in the 200 mW regime with an excellent beam quality were achieved.

Single mode lasing in a gain-guided index anti-guided diode end pumped fiber

Abstract: Single mode oscillation in a 200 mum core diameter gain guided index anti-guided fiber laser is demonstrated. Single mode oscillation is maintained for pumping of up to four times laser threshold, limited by available pump power.