Raymond Thorson Newell

Planetary Geochemical Investigations Using Raman and Laser-Induced Breakdown Spectroscopy

An integrated Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) instrument is a valuable geoanalytical tool for future planetary missions to Mars, Venus, and elsewhere. The ChemCam instrument operating on the Mars Curiosity rover includes a remote LIBS instrument. An integrated Raman-LIBS spectrometer (RLS) based on the ChemCam architecture could be used as a reconnaissance tool for other contact instruments as well as a primary science instrument capable of quantitative mineralogical and geochemical analyses. Replacing one of the ChemCam spectrometers with a miniature transmission spectrometer enables a Raman spectroscopy mineralogical analysis to be performed, complementing the LIBS chemical analysis while retaining an overall architecture resembling ChemCam. A prototype transmission spectrometer was used to record Raman spectra under both Martian and Venus conditions. Two different high-pressure and high-temperature cells were used to collect the Raman and LIBS spectra to simulate surface conditions on Venus. The resulting LIBS spectra were used to generate a limited partial least squares Venus calibration model for the major elements. These experiments demonstrate the utility and feasibility of a combined RLS instrument.

Loading dynamics of optical trap and parametric excitation resonances of trapped atoms

We study the loading dynamics of an optical dipole trap and an optical lattice both experimentally and theoretically. A simple power dependence for the number of trapped atoms (N∝P3∕2) is revealed in both cases. We then study the parametric excitation of the trapped atoms. High order parametric resonance is observed close to but lower than 4ν in a CO2 laser optical lattice. The existence of the high harmonic and its shift toward lower frequency are attributed to the anharmonicity of the optical trapping potential. We investigate the discrepancy between experimentally measured optical lattice frequencies and the theoretical calculation for several published experiments and present corrected formula for trap frequency calculations. Using this corrected formula and accounting for the off-center lattice sites, we present a modified formula for calculating the optical lattice frequency and obtain better agreement between experimental measurement and theoretical calculation.

Network-Centric Quantum Communications

Network-centric quantum communications (NQC) - a new, scalable instantiation of quantum cryptography providing key management with forward security for lightweight encryption, authentication and digital signatures in optical networks - is briefly described.

Novel fiber-optic geometries for fast quantum communication

Recent experiments have generated great interest in combined wavlength (WDM) and spatial (SDM) divison multiplexing using optical angular momentum (OAM) at data rates orders of magnitude better than current telecommunication standards. We discuss here a class of novel fiber optic devices that induce mode coupling along the optical axis of the fiber by sinusoidally varying the refractive index. Using the analogy between the wave equation for weakly guiding fibers and the paraxial equation, we review fibers that support Laguerre-Gauss modes and, motivated by these works, demonstrate that similar fibers with different core shapes support Hermite-Gauss modes in the same regime. Finally, we utilize these relations to demonstrate how one might generate different orbital angular momentum states using induced coupling between Hermite-Gauss modes, motivated by the works of many previous authors. We further describe a class of devices that could generate either a mode with a defined orbital angular momentum, and support its propagation along a fiber, or create a superposition of modes from a single modal input. Previous efforts focused on the generation of OAM states in a fiber have required extremely exotic refractive index profiles, and we present here a method based on already developed refrative index profiles and manipulation techniques, specifically using fiber bragg gratings to drive modal coupling in a fiber, in an effort to generate states with well defined OAM.