Optoelectronic

A novel synthesis method is presented for the preparation of nanosized-semiconductor zinc oxide-sulphide (ZnO/ZnS) core-shell nanocomposites, both formed sequentially from a single-source solid precursor. ZnO nanocrystals were synthesized by a simple co-precipitation method and ZnO/ZnS core-shell nanocomposites were successfully fabricated by sulfidation of ZnO nanocrystals via a facile chemical synthesis at room temperature. The as-obtained samples were characterized by X-ray diffraction and transmission electron microscopy. The results showed that the pure ZnO nanocrystals were hexagonal wurtzite crystal structures and the ZnS nanoparticles were sphalerite structure with the size of about 10 nm grown on the surface of the ZnO nanocrystals. Optical properties measured reveal that ZnO/ZnS core-shell nanocomposites have integrated the photoluminescent effect of ZnO and ZnS. Based on the results of the experiments, a possible formation mechanism of ZnO/ZnS core-shell nanocomposites was also suggested. This treatment is suggested to improve various properties of optoelectronically valuable ZnO/ZnS nanocomposites. These nanosized semiconductor nanocomposites can form a new class of luminescent materials for various applications.

ABSTRACTAn all fiber linear frequency modulated continuous wave (FMCW) coherent laser radar system is under development with a goal to aide NASA's new Space Exploration initiative for manned and robotic missions to the Moon and Mars. Linear FMCW lidar has the capability of high resolution range measurements, and when configured into a multi-channel receiver system it has the capability of obtaining high precision vector velocity measurements. Precision range and vector velocity data are beneficial to navigating planetary landing pods to the pre-selected site and achieving autonomous, safe soft-landing. This paper discusses the design of a second generation prototype system under development at NASA Langley Research Center and presents preliminary performance data obtained from field experiments.

ABSTRACTThis paper discusses the prospects of silicon as a Mid-wave Infra-red Raman crystal. As a specific example of novel devices that can be realized, we introduce the concept of multi-mode silicon Raman amplifiers and their application in infrared image pre-amplification. The same technology also has application in incoherent beam combining.