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Multiple variants of the Diode Pumped Alkali Laser (DPAL) have recently been demonstrated at the Air Force Research Laboratory (AFRL). Highlights of this ongoing research effort include: a) a 571W rubidium (Rb) based Master Oscillator Power Amplifier (MOPA) with a gain (2α) of 0.48 cm-1, b) a rubidium-cesium (Cs) Multi-Alkali Multi-Line (MAML) laser that simultaneously lases at both 795 nm and 895 nm, and c) a 1.5 kW resonantly pumped potassium (K) DPAL with a slope efficiency of 50%. The common factor among these experiments is the use of a flowing alkali test bed.

A metastable argon laser operating at 912 nm has been demonstrated by optically pumping with a pulsed titanium sapphire laser to investigate the temporal dynamics of an Advanced Noble Gas Laser (ANGL). Metastable argon concentrations on the order of 1011 cm-3 were maintained with the use of a radio frequency (RF) capacitively coupled discharge. The end-pumped laser produced output powers under 2 mW of average power with pulse lengths on the order of 100 ns. A comparison between empirical results and a four level laser model using longitudinally average pump and inter-cavity intensities is made. An alternative, highly-efficient method of argon metastable production for ANGL was explored using carbon nanotube (CNT) fibers. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Magnetic resonance imaging may be extended by various orders of modulation-encodings to acquire simultaneously FID data-sets representing very high dimensionality. For example, we may encode three spatial-position dimensions, three molecular-velocity dimensions, a chemical shift dimension, three perfusive flow dimensions, and so on. Careful observation on even the common 2D-MRI scans, however, yield some puzzling results about the behavior of contrast/detail detectability. The multi-dimensional options and capabilities of MRI arise because the physical system inherently is an interferometric data-acquisition modality. There is a "hidden" dimension in the data-acquisition, namely, the resolution scale of digitization of the FID-data values. This dimension implies requirements on the dynamic-range of the data-acquisition, just as the Nyquist-limit implies requirements on the fineness of the temporal sampling mesh. One must account for the limitations so imposed. We propose here a new quantitative imaging descriptor, the Detail-in-Image to Totality-in-object Ratio (DITOR), whose values impose limitations upon the system dynamic-range required. These limitations become more severe as the imaging dimensionality becomes larger, and MRI system behavior in this regard is very different from ordinary x-ray medical imaging. This paper shows several examples of phantom and human studies which may well illustrate the limitations implied by DITOR, and develops the role of stochastic noise contributions to the DITOR requirements.© (1986) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

If any data compression scheme for medical images shows some level of success, then this necessarily implies information redundancy in the image data. The information capacity of the system therefore must be larger than the information content. A powerful way to analyze and exploit the possibilities for optimum data-compression, transmission methods, and other useful image-processing options is to seek the eigenfunction representation of the image. By transforming the image-data into the eigen-representation, we obtain a transformed image array (the q-space image) which is the irreducible representation of the data for that imaging system. The coefficients of the irreducible representation are, in the parlance of information theory, "non-interfering symbols". Preliminary studies show that the eigen-representation allows immediate, direct, and predictable compression of the system data capacity to the image data information content. Our analysis of medical images from magnetic resonance imaging (MRI) scans has allowed us to demonstrate some specific data-compression strategies which will be most beneficial, rapid and flexible for PACS applications