We demonstrate high output power UVC-LEDs from 230 to 237 nm on AlN single-crystal substrates. The UVC-LEDs show a single peak in the electroluminescence spectrum, from 20 to 300 mA. Forward voltages were typically ∼7 V at 100 mA while measured initial output powers at 237 nm, 235 nm, 233 nm and 230 nm were 2.2 mW, 1.9 mW, 1.5 mW and 1.2 mW, respectively. At 20 mA, the measured wall-plug efficiencies were 0.37%, 0.32%, 0.25% and 0.19% at the same wavelengths, respectively. These devices have demonstrated over 3600 h of lifetime operating at 20 mA.

Highly efficient, reliable packaging of semiconductor optical devices such as lasers and optical amplifiers remains an expensive and challenging task. In this paper, we present an approach to singlemode fiber coupling which results in relaxed alignment tolerances during the package assembly process, while maintaining coupling efficiencies as high as 34-40%. In addition, the approach provides some versatility with respect to the placement of passive optical components inside the package.

Experimental studies have been performed on several aspects of the degradation of electroluminescent quantum efficiency in ZnO-doped GaP light-emitting diodes. The dependence of degradation on stress temperature, stress current (experienced during accelerated aging), and measurement current (at which quantum efficiency is evaluated) has been empirically determined from experiments on several lots of devices. It is shown that degradation is dominated by a decrease in bulk p-side radiative recombination efficiency. The degradation of other factors (such as injection efficiency and injection ratio) contributing to the overall electroluminescent efficiency has only a secondary effect. Moreover, it is shown empirically that the dependences of degradation on temperature and stress current are separable.

A tapered fiber bundle is one of the leading approaches to coupling pump light into claddingpumped fibers. This article compares it to other pump coupling schemes, and describes the tapered fiber bundle in detail. In addition tapered fiber bundles which maintain the polarization state of the signal and transform the size of the mode are described.

No abstract