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The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically-pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ~1000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications., Comment: 10 pages, 3 figures

Formation and emission of soot and polycyclic aromatic hydrocarbons (PCAH) from a turbulent continuous flow combustor have been studied. Measurements included mass concentration of both soot and PCAH, composition of individual PCAH, and size distribution of soot particles, as a function of mixing intensity, fuel equivalence ratio and type of fuel (kerosene or benzene). Both soot and PCAH concentrations reach maxima early in the flame, after which PCAH decays rapidly and soot decays much slower. The maximum PCAH concentration always preceded that of soot in agreement with the concept that certain PCAH may serve as intermediates in soot formation. An approximate calculation based on the assumptions of local equilibrium with respect to soot formation and a Gaussian distribution of air-fuel mixedness gave satisfactory correlations of the data on soot formation at the higher cold gas velocity. At the lower velocity, the amount of soot and PCAH formed was drastically increased and strongly dependent on fuel atomization.

Statistical model of distribution of federal expenditures among states