RESUMO
In this paper, the self-absorption of InGaN quantum wells at high photon density is studied based on a rectangular ridge structure. The ridge structure was fabricated based on a standard GaN-based blue LED wafer grown on (0001) patterned sapphire substrate. The high-density photons were obtained by a high-power femtosecond laser with high excitation of 42kW/cm2 at room temperature. Based on the analysis of the photoluminescence intensities of the InGaN quantum wells, we found that the absorption coefficient of the InGaN quantum wells varies with the background photon density. The results revealed that the final absorption coefficient of the InGaN quantum well decreases with the increase of photon density, which can be 48.7% lower than its normal value under our experimental conditions.
RESUMO
Seasonal and spatial distributions of total mercury (THg) in the Danshuei Estuary and adjacent coastal areas near the ocean outfall of Taipei, Taiwan, have been successfully investigated from May 2003 to January 2005. We found spatio-temporal variation in THg levels in the Danshuei coastal area was the result of sources and supplies of Hg. High THg concentrations in sediments and seawater were particularly found near the effluent outfall. Average THg levels (avg.: 9-22 ng L-1) were much higher than those in surrounding coastal seawaters (avg.:1-2 ng L-1). Organic carbon contents then played vital roles in controlling water and sedimentary Hg concentrations and occurrences. Hg enrichment factor (EF) as an index of contamination status in surface sediments of the Danshuei coastal area averaged 2.0 ± 0.8 (EFs > 1), indicating an extra non-crustal source from anthropogenic loadings. It implies the Dansheui coastal environment nearby the sewer outfall is facing Hg pollution.