There is a longstanding, and largely unexplained, correlation between the laser damage susceptibility of optical components and both the surface quality of the optics, and the presence of near surface fractures in an optic. In the present work, a combination of acid leaching, acid etching, and confocal time resolved photoluminescence (CTP) microscopy has been used to study laser damage initiation at indentation sites. The combination of localized polishing and variations in indentation loads allows one to isolate and characterize the laser damage susceptibility of densified, plastically flowed and fractured fused silica. The present results suggest that: 1) laser damage initiation and growth are strongly correlated with fracture surfaces, while densified and plastically flowed material is relatively benign, and 2) fracture events result in the formation of an electronically defect rich surface layer which promotes energy transfer from the optical beam to the glass matrix.
The new realities of the healthcare marketplace are forcing healthcare decision makers to implement innovative operational philosophies, techniques, and tools that were proven in other industries to enhance the effectiveness of their organization. This study examines the acceptance and effectiveness of these philosophies, techniques, and tools in a hospital operational setting. The impact of implementation on operational and strategic outcomes is examined for 108 hospitals. Overall, the results of this study appear to indicate that certain quality improvement philosophies, techniques, and tools have been successful when applied in a hospital operational setting.
High average power, diode pumped petawatt laser systems: a new generation of lasers enabling precision science and commercial applications,"
New advances in cathodoluminescence (CL) instrumentation allow more advanced characterisation of compound semiconductor materials and devices. CL offers the advantage of combined high spatial and spectral information in one experiment. However, until now, CL results have typically been two dimensional, in the form of images at discrete wavelengths, or spectra chosen from specific points on the specimen. Spectrum Imaging allows large data sets to be collected with relative ease so that the full spectroscopic information can be recorded at every pixel position in an image. Gaussian fitting and advanced subtraction techniques are shown to be valuable in mapping spectral shifts, peak widths, and in the extraction of hidden luminescence features. This helps characterise important luminescence features such as impurities, doping, stress, extended defects, and alloy and quantum confinement inhomogeneities.Introduction Cathodoluminescence (CL) is the emission of photons from a specimen stimulated using an electron beam. The CL emitted is governed by competition between non-radiative and radiative electron-hole pair recombination events. In the field of compound semiconductors, where the ability to emit and detect photons efficiently and of a specific wavelength is of paramount importance in their application, CL is increasingly used as a research and evaluation tool. The growth in the application ranges from materials and growth characterisation through to device design and failure analysis.The technique has the advantage of giving relatively high spatial resolution results using a flexible injection source. In a scanning electron microscope (SEM or STEM) the electron probe is easy to control in terms of position, focusing, energy and flux. In addition it has a high depth of field so can cope with complex structures, and takes place in a vacuum which is ideal for cryogenic temperatures. The spatial resolution which is achievable is dependent on the specimen, microscope and CL equipment. Recent results have demonstrated resolution in the range of 20 nm [1]. CL performed in a transmission electron microscope also offers the promise of high spatial resolution due to the reduced dimensions of the generation volume for a thin TEM sample.Growth in CL as a technique has matched advances in the importance of compound semiconductors and has been associated with advances in electron microscope and cathodoluminescence technology. Early CL studies were primarily limited to panchromatic imaging. This simple method of collecting and detecting luminescence without recourse to dispersion or filtering remains valuable, especially in terms of mapping non radiative recombination sites.Spectral CL has gained in popularity over the last decade. The most favoured and successful approach involves direct optical coupling between a specimen, a monochromator, and finally a photo-multiplier
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