High-power, high-brightness, tunable GaSb-based VECSEL at 2.X μm
High-power, high-brightness, tunable GaSb-based VECSEL emitting in the 2.0-2.4 μm wavelength range is characterized. CW output power vs. absorbed pump power of a diamond-bonded 2.3 μm VECSEL for several heat sink temperatures is studied. Finite element model is used to analyze the heat transport in a GaSb-based VECSEL with an intracavity diamond heatspreader. The tuning characteristics of the VECSEL is also studied.
High-power (>0.5-W CW) diode-pumped vertical-external-cavity surface-emitting semiconductor lasers with circular TEM/sub 00/ beams
We report demonstration of a new high-power semiconductor laser technology, the optically pumped semiconductor (OPS) vertical-external-cavity surface-emitting laser (VECSEL). Using diode laser pump, an OPS-VECSEL laser with a strain-compensated InGaAs-GaAsP-GaAs multiquantum-well (MQW) structure operated continuous-wave (CW) near /spl lambda//spl sim/1004 nm with record output power of 0.69 W in a TEM/sub 11/ mode, 0.52 W in a TEM/sub 00/ mode, and 0.37 W coupled to a single-mode fiber. It is feasible to produce greater than 1 W of power in a diffraction-limited circular beam from an efficient, compact, manufacturable and reliable OPS-VECSEL laser.
The Limits of Vulnerability in Explaining Fear of Crime: A Comparative Neighborhood Analysis
Recent research on the fear of crime in the United States has focused on the sources of fear. Many of these studies have identified neighborhood-level variables that are related to fear, but most have examined the differences in fear among individual residents of one or more cities. There has been substantially less research on the differences in the sources of fear among residents of different areas within a single city. This article examines the causes of fear through a comparative analysis of three different neighborhoods in San Francisco. An analysis of covariance model is used to assess the importance of differences in the sources of fear that may be associated with an individual's neighborhood of residence. The findings demonstrate that age, as a measure of physical vulnerability previously associated with fear among individuals, is not related to fear in neighborhoods where residents express the greatest general concern about crime. It is concluded that in those urban areas where crime problems are regular features of the neighborhood environment, measures of physical vulnerability are less important in predicting differences in fear among individuals.