archives@tulane.edu / This dissertation details a measurement of the n-$^{4}$He coherent scattering length to be $b_{4\rm{He}} = [3.0982 \pm\: 0.00214\; (\rm{stat}) \pm\: 0.00077\; (\rm{sys})]$ fm utilizing a perfect silicon crystal neutron interferometer. This measurement provides over a factor of 10 improvement in precision and differs by $0.162$ fm compared to the most commonly used value. Neutron interferometry provides a tool for precision scattering lengths measurements for a variety of isotopes. Examples include coherent scattering length measurements for $^{1}$H, $^{2}$H, $^{3}$He and the incoherent scattering length of $^{3}$He. Neutron scattering lengths of light nuclei provide useful tests of nuclear potential models and serve as inputs for nuclear effective field theories. A monolithic, perfect silicon neutron interferometer splits the wave function of a single neutron via Bragg diffraction into two coherent paths spatially separated to the extent of a few centimeters. A sample of $^{4}$He gas, contained within an aluminum cell, is introduced into one beam path which produces a phase shift directly proportional to $b_{4\rm{He}}$. Significant effort has been spent quantifying important systematic considerations that include thermal transfer from the gas cell to the interferometer crystal and deformation of the gas cell walls due to gas pressure which ranges from 7 bar to 13 bar which were calculated by an FEA simulation. Thermal transfer between the gas cell and interferometer crystal induces a change of the intrinsic interferometer phase which is dependent on sample position. This additional systematic phase has been named the shadow phase. A glycol cooling system was used to mitigate the shadow phase and a special measurement pattern was devised to account for possible shadow phase drift. This work was performed at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). / 1 / Robert Haun

A simple model for optical pulse propagation in a nondegenerate two-level amplifying medium is considered, under the assumption of extreme Doppler broadening. Starting with a "Pade approximant" left reflection coefficient with N simple poles and N$\sb{\rm b}\leq$ N bound states, and employing Lamb's one-component inverse scattering method*, pulses whose initial area can be $>\pi$ are obtained. Then, employing the asymptotic behavior of the eigenvalues of the kernel of the right Marchenko equation, the asymptotic behavior of the pulses far into the medium is analyzed in detail when N $\leq$ 3. In addition to the expected portion of area $\pi$ near the light cone which undergoes amplification and compression, pulses with a continuous leading edge develop forward-moving oscillations, and some pulses trail behind one or more 2$\pi$ (or 0$\pi$) solitons. Pulses whose final area is $\pi$, 3$\pi$, and 5$\pi$ are obtained. Interestingly, the number of trailed solitons is in general not equal to the number of bound states. These solitons are associated with a subset of the zeroes of the transmission coefficient rather than of its poles. Conditions for the appearance of a soliton are given in terms of the poles and residues of the left reflection coefficient. A connection is established between the values of the pulse profiles and their first 2N $-$ 1 derivatives at the light cone, and the residue and pole parameters of the left reflection coefficient. For N = 2 and the case in N = 3 where the pulse has a continuous leading edge, simple conditions for the appearance of a soliton are obtained in terms of the values of the pulse profiles and their first N $-$ 1 derivatives at the light cone, and the poles of the left reflection coefficient. It is established for N $\leq$ 3 that for each 2$\pi$ soliton there is a purely imaginary zero of the left reflection coefficient / in the lower half $\nu$ plane and that for a 0$\pi$ soliton there are a pair of zeroes of the left reflection coefficient lying symmetrically about the negative imaginary $\nu$ axis. ftn*G. L. Lamb, Jr., Phys. Rev. A 12, 2052 (1975). / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0806. / Major Professor: J. Daniel Kimel. / Thesis (Ph.D.)--The Florida State University, 1987.

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Quantum optics provides powerful means to probe quantum mechanics. In this thesis, we study various aspects of quantum phenomena arising in quantum optical systems. Part I studies broadband quantum teleportation. After presenting three different methods of analyzing the standard teleportation protocol, we study the interplay between various bandwidths in determining the fidelity of a broadband quantum field teleportation. Explicit formulae for the degrees of first- and secondorder coherence for the teleportation of resonance fluorescence are derived for this purpose. Part II studies entanglement arising in cascaded open quantum (optical) systems. First, a detailed laser model is produced within quantum trajectory theory to study the total decoherence rate of a laser-driven qubit. Second, using this model, we address the issue of laser quantum state, viewed in connection with separability of the laser-driven-qubit system. Third, a measure of entanglement within quantum trajectory theory called ‘Contextual Entanglement’ is calculated for a few simple systems and compared with the ‘Entanglement of Formation’. Lastly, we introduce a method to quantify entanglement (based on the contextual entanglement) between a source and the field it emits, which we call the ‘Entanglement Spectrum’. It is applied to study the entanglement between a laser-driven qubit and the field the qubit scatters.

Thesis (Ph. D.)--University of Chicago, 1911. / "Private edition, distributed by the University of Chicago Libraries, Chicago, Illinois, 1911." Includes bibliographical references. Also available on the Internet.

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Nanoshells (NS) and nanoparticles (NP) are tunable plasmonic particles that can be precisely engineered for specific applications including surface enhanced spectroscopies. A new, general method for the synthesis of core-shell and solid nanoparticles has been developed and is presented. Based on the CO reduction of Au3+, this new process yields the highest quality gold nanoshells synthesized to date. The constraints on precursor lifetime have been relaxed and post-synthesis purification has been eliminated. Nonresonant surface enhanced Raman optical activity (SEROA) has been investigated using biomolecular analytes deposited on Au nanoshell or nanoparticle substrates. The first, and currently the only, near-infrared (780 nm) excited scattered circular polarization Raman optical activity spectrometer (NIROAS) has been constructed. Surface enhanced Raman optical activity spectroscopy has been validated by the collection of symmetrical, surface enhanced, signed circular polarization intensity difference spectra from several test molecules including, (S)- and (R)-tryptophan, and (SS)- and (RR)-phenylalanine-cysteine.

Metallic nanostructures are one of the most versatile tools available for manipulating light at the nanoscale. These nanostructures support surface plasmons, which are collective excitations of the conduction electrons that can exist as propagating waves at a metallic interface or as localized excitations of a nanoparticle or nanostructure. Plasmonic structures can efficiently couple energy from freely propagating electromagnetic waves to localized electromagnetic fields and vice-versa, essentially acting as an optical antenna. As a result, the intensity of the local fields around and inside the nanostructure are strongly enhanced compared to the incident radiation. In this thesis, this ability to manipulate electromagnetic fields on the nanoscale is employed to control a wide range of optical phenomena. These studies are performed using structures based on metallic nanoshells, which consist of a thin Au shell coating a silica nanosphere. To investigate the parameters controlling the plasmonic response of metallic nanoshells, two changes to the nanoshell composition are studied: (1) the Au shell is replaced with Cu which has interband transitions that strongly influence the plasmon resonance, and (2) the silica core is replaced by a semiconducting Cu 2O core which has a significantly higher dielectric constant and non-trivial absorbance. The focusing of electromagnetic energy into intense local fields by plasmonic nanostructures is then directly investigated by profiling the nanoshell near field using a Raman-based molecular ruler. Next, plasmons supported by Au nanoshells are used to control the fluorescence of near-infrared fluorophores placed at controlled distances from the nanoshell surface. In this context, the analogy of an optical antenna is very relevant: the enhanced field at the surface of the nanoshell increases the absorption of light by the fluorophore, or equivalently couples propagating electromagnetic waves into a localized receiver, while the large scattering cross section enhances the coupling of energy from a localized source, the fluorophore, to far-field radiation. Excellent agreement with models based on Mie theory is achieved for both Raman and fluorescence. Experimentally measured enhancements of the radiative decay rate for fluorophores on Au nanoshells and Au nanorods are also consistent with this model. Plasmonic nanostructures can also control the flow of light into larger structures. This is observed by measuring the nanoparticle-induced enhancement and suppression of photocurrent in a silicon photodiode is at the single particle level for silica nanospheres, Au nanospheres, and two types of Au nanoshell Finally, the simultaneous physical manipulation of an individual plasmonic nanostructure on the few-nanometer scale using light and detection of the local electromagnetic field during this ongoing process with the same incident beam is performed. For this experiment, a Au nanoshell is separated from a metallic surface by a few-nanometer thick polymer layer to form a nanoscale junction, or nanogap Illuminating this structure with ultrashort optical pulses, exciting the plasmon resonance, results in a continuous, monitorable collapse of the nanogap. An easily detectable four-wave mixing (FWM) signal is simultaneously generated by this illumination of the nanogap, providing a continuous, highly sensitive optical monitor of the nanogap spacing while it is being optically reduced. The dramatic increase in this signal upon contact provides a clear, unambiguous signal of the gap closing.