Neutralizer and sample chamber for the Atomic Oxygen Simulation System (AOSS)

A neutralizer system capable of converting a beam of oxygen ions (O(+) or O2(+)) into a beam of low-energy neutral oxygen atoms (O) was developed. The neutralizer system is to be designed to be compatible with the Atomic Oxygen Simulation System (AOSS) located in the Physical Science Branch of MSFC. The Center for Molecular and Atomic Studies at Surfaces (CMASS) at Vanderbilt University has met these objectives by developing a system that neutralizes the ions through electron transfer during a grazing-incidence reflection of an ion beam from a smooth nickel surface. The purpose is to describe the system, provide schematic representations of the system, and to discuss the use of the system in relation to the AOSS at the Physical Science Branch of MSFC

Optics and Quantum Electronics

Contains table of contents for Section 3 and reports on eighteen research projects.Defense Advanced Research Projects Agency/MIT Lincoln Laboratory Contract MDA972-92-J-1038Joint Services Electronics Program Grant DAAH04-95-1-0038National Science Foundation Grant ECS 94-23737U.S. Air Force - Office of Scientific Research Contract F49620-95-1-0221U.S. Navy - Office of Naval Research Grant N00014-95-1-0715MIT Center for Material Science and EngineeringNational Center for Integrated Photonics Technology Contract DMR 94-00334National Center for Integrated Photonics TechnologyU.S. Navy - Office of Naval Research (MFEL) Contract N00014-94-1-0717National Institutes of Health Grant 9-R01-EY11289MIT Lincoln Laboratory Contract BX-5098Electric Power Research Institute Contract RP3170-25ENEC

Near Field Optical Microscopy Imaging with a Free Electron Laser in the 1-10 Micron Spectral Range: Overview and Perspectives

The need to image objects on increasingly finer scales and spatially localized specific molecules can be met by the combination of infrared, visible and Raman spectroscopy with scanning near-field microscopy, giving rise to a powerful nanospectroscopic tool used to perform simultaneous topographical measurements and optical/chemical characterization with subwavelength resolution, overcoming the diffraction limit of light. Conventional spectroscopy is often not enough sensitive and spatially resolved to detect specific elements or domains in a sample. Scanning near-field optical microscopy is a sensitive and flexible technique that achieves an enhanced optical resolution through the very close placement of the sensing element to the object. We present several results of near field spectroscopy with infrared radiation emitted by a free electron laser to investigate material science and biological samples. The local reflectivity revealed features, as a function of photon energy, that were not present in the corresponding shear-force (topology) images and were due to localized changes in the bulk properties of the sample. The size of the smallest detected features clearly demonstrated that near-field conditions were reached, with an optical spatial resolution well below the diffraction limit

Photobleaching-free infrared near-field microscopy localizes molecules in neurons

High-resolution detection of specific molecules in cells is a major challenge in biology. We show that infrared scanning near-field microscopy can detect the spatial distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid–type glutamate receptor clusters on hippocampal neurons. The GluR2 subunits were labeled with the die Alexa 488 and high-resolution infrared micrographs were taken at 6.25 µm. The absence of photobleaching makes this approach suitable for a long-term observation and allows to localize different infrared-absorbing molecules over the complex background of other cell components

Depth dependent modification of optical constants arising from H+ implantation in n-type 4H-SiC measured using coherent acoustic phonons

Silicon carbide (SiC) is a promising material for new generation electronics including high power/high temperature devices and advanced optical applications such as room temperature spintronics and quantum computing. Both types of applications require the control of defects particularly those created by ion bombardment. In this work, modification of optical constants of 4H-SiC due to hydrogen implantation at 180 keV and at fluences ranging from 1014 to 1016 cm−2 is reported. The depth dependence of the modified optical constants was extracted from coherent acoustic phonon spectra. Implanted spectra show a strong dependence of the 4H-SiC complex refractive index depth profile on H+ fluence. These studies provide basic insight into the dependence of optical properties of 4H silicon carbide on defect densities created by ion implantation, which is of relevance to the fabrication of SiC-based photonic and optoelectronic devices