Physics Commons^™

Absorption-Induced Trapping In An Anisotropic Magneto-Optical Trap, Joel A. Greenberg, M. Oria, Andrew M.C. Dawes, Daniel J. Gauthier

Andrew M C Dawes

We report on a simple anisotropic magneto-optical trap for neutral atoms that produces a large sample of cold atoms confined in a cylindrically-shaped volume with a high aspect ratio (100:1). Due to the large number of trapped atoms, the laser beams that propagate along the optically thick axis of the trap to cool the atoms are substantially attenuated. We demonstrate that the resulting intensity imbalance produces a net force that spatially localizes the atoms. This limits both the trap length and the total number of trapped atoms. Rotating the cooling beams by a small angle relative to the trap axis …

Distortion Management In Slow-Light Pulse Delay, Michael D. Stenner, Mark A. Neifeld, Zhaoming Zhu, Andrew M.C. Dawes, Daniel J. Gauthier

Andrew M C Dawes

We describe a methodology to maximize slow-light pulse delay subject to a constraint on the allowable pulse distortion. We show that optimizing over a larger number of physical variables can increase the distortion-constrained delay. We demonstrate these concepts by comparing the optimum slow-light pulse delay achievable using a single Lorentzian gain line with that achievable using a pair of closely-spaced gain lines. We predict that distortion management using a gain doublet can provide approximately a factor of 2 increase in slow-light pulse delay as compared with the optimum single-line delay. Experimental results employing Brillouin gain in optical fiber confirm our …

780 Nm Diode Lasers For Atomic Physics, Bryson Vivas, Simone Carpenter, Jenny Novak, Andrew M. C. Dawes

Andrew M C Dawes

This poster presents the results of the summer research project conducted by Bryson Vivas, Simone Carpenter, and Jenny Novak. The research was supervised by Dr. Andrew Dawes and conducted in the Photonics and Quantum Optics Lab of Pacific University.

Simultaneous Quantum-State Measurements Using Array Detection, Andrew Dawes, Mark Beck

Andrew M C Dawes

We have simultaneously measured the quantum states of two different spatial modes of the same optical beam by performing quantum-state tomography with an array detector. Both modes are well described by coherent states, but the projection of the signal onto the local oscillator mode contains a mean of 0.09 photons, while a more complicated mode has a mean of 4.3 photons. This demonstrates that for this particular mode the effective detection efficiency when using array detection is over 40 times greater than when using single detectors.

Direct Observation Of Optical Precursors In A Region Of Anomalous Dispersion, Heejeong Jeong, Andrew M.C. Dawes, Daniel J. Gauthier

Andrew M C Dawes

We create optical precursors by propagating a step-modulated optical pulse through a linear resonant dielectric absorber. The field emerging from the dielectric consists of a several-nanosecond-long spike with near 100% transmission, which decays to a constant value expected from Beer’s law. This high transmission spike might be useful for imaging applications requiring penetrating optical radiation. We compare our observations to two different theories, revealing that the spike consists of both the Sommerfeld and Brillouin precursors.

All-Optical Switching With Transverse Optical Patterns, Andrew M.C. Dawes, Lucas Illing, Joel A. Greenberg, Daniel J. Gauthier

Andrew M C Dawes

We demonstrate an all-optical switch that operates at ultra-low-light levels and exhibits several features necessary for use in optical switching networks. An input switching beam, wavelength λ, with an energy density of 10−2 photons per optical cross section [σ=λ2 / (2π)] changes the orientation of a two-spot pattern generated via parametric instability in warm rubidium vapor. The instability is induced with less than 1 mW of total pump power and generates several μWs of output light. The switch is cascadable: the device output is capable of driving multiple inputs, and exhibits transistor-like signal-level restoration with both saturated and intermediate response …

Using Transverse Optical Patterns For Ultra-Low-Light Optical Switching, Andrew M.C. Dawes

Andrew M C Dawes

All-optical devices allow improvements in the speed of optical communication and computation systems by avoiding the conversion between the optical and electronic domains. The focus of this thesis is the experimental investigation of a new type of all-optical switch that is based on the control of optical patterns formed by nonlinear interactions between light and matter. The all-optical switch consists of a pair of light beams that counterpropagate through warm rubidium vapor. These beams induce a nonlinear optical instability that gives rise to mirrorless parametric self-oscillation and generates light in the state of polarization that is orthogonal to that of …

Mode Optimization For Quantum-State Tomography With Array Detectors, Andrew M. Dawes, Mark Beck, K. Banaszek

Andrew M C Dawes

We demonstrate that it is possible to choose an optimal signal mode for state reconstruction when performing quantum-state tomography with array detectors. The mode optimization is done during the data analysis ~i.e., after all the data have been collected.! We develop theoretically a procedure for finding the mode that satisfies a criterion which is quadratic in field operators; as examples we explicitly show how to maximize the average photon number, or the amount of quadrature squeezing. We experimentally demonstrate the technique by finding the mode which maximizes the average photon number for coherent-state signal beams occupying both linear and sinusoidal …

Optical Switching With Cold Atoms, Andrew Dawes

Andrew M C Dawes

A Viewpoint on: Efficient All-Optical Switching Using Slow Light within a Hollow Fiber M. Bajcsy, S. Hofferberth, V. Balic, T. Peyronel, M. Hafezi, A. S. Zibrov, V. Vuletic, and M. D. Lukin Phys. Rev. Lett. 102, 203902 (2009) – Published May 18, 2009

Broadband Sbs Slow Light In An Optical Fiber, Zhaoming Zhu, Andrew M.C. Dawes, Daniel J. Gauthier, Lin Zhang, Alan E. Willner

Andrew M C Dawes

In this paper, we investigate slow light via stimulated Brillouin scattering (SBS) in a room temperature optical fiber that is pumped by a spectrally broadened laser. Broadening the spectrum of the pump field increases the linewidth Δωp of the Stokes amplifying resonance, thereby increasing the slow-light bandwidth. One physical bandwidth limitation occurs when the linewidth becomes several times larger than the Brillouin frequency shift ΩB so that the anti-Stokes absorbing resonance substantially cancels out the Stokes amplifying resonance and, hence, the slow-light effect. We find that partial overlap of the Stokes and anti-Stokes resonances can actually lead to an enhancement …

Effects Of Localized Trap-States And Corrugation On Charge Transport In Graphene Nanoribbons, Oleksiy Roslyak, Upali Aparajita, Godfrey Gumbs, Danhong Huang

Publications and Research

We investigate effects of the electron traps on adiabatic charge transport in graphene nanoribbons under a longitudinal surface acoustic wave (SAW) potential. Due to the weak SAW potential and strong transverse confinement of nanoribbons, minibands of sliding tunnel-coupled quantum dots are formed. Therefore, as the chemical potential passes through minigaps, quantized adiabatic charge transport is expected to occur. We analyze the condition for a closed minigap, thereby destroying the current quantization in a nanoribbon. We present numerical calculations showing the localized energy states within minigaps. Additionally, we compare the results with the minibands of corrugated nanoribbons.

Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman

Physics and Astronomy Faculty Publications

An optically and geometrically thick torus obscures the central engine of active galactic nuclei (AGN) from some lines of sight. From a magnetohydrodynamical framework, the torus can be considered to be a particular region of clouds surrounding the central engine where the clouds are dusty and optically thick. In this framework, the magnetic field plays an important role in the creation, morphology and evolution of the torus. If the dust grains within the clouds are assumed to be aligned by paramagnetic alignment, then the ratio of the intrinsic polarization and visual extinction, P(per cent)/A_v, is a …

The X-Ray Properties Of Optically Selected Clusters Of Galaxies, A. K. Hicks, G. W. Pratt, M. Donahue, E. Ellingson, M. Gladders, H. Böhringer, H. K. C. Yee, Renbin Yan, J. H. Croston, D. G. Gilbank

Physics and Astronomy Faculty Publications

We present the results of Chandra and Suzaku X-ray observations of nine moderate-redshift (0.16 < z < 0.42) clusters discovered via the Red-sequence Cluster Survey (RCS). Surface brightness profiles are fitted to β-models, gas masses are determined, integrated spectra are extracted within R₂₅₀₀, and X-ray temperatures and luminosities are inferred. TheL_X–T_X relationship expected from self-similar evolution is tested by comparing this sample to our previous X-ray investigation of nine high-redshift (0.6 < z < 1.0) optically selected clusters. We find that optically selected clusters are systematically less luminous than X-ray selected clusters of similar X-ray temperature at both moderate and high z. We are unable to constrain evolution in the L_X–T_X relation with these data, but find it consistent with no evolution, within relatively large uncertainties. To investigate selection effects, we compare the X-ray properties of our sample to those of clusters in the …

Modeling A Sensor To Improve Its Efficacy, Nabin K. Malakar, Daniil Gladkov, Kevin H. Knuth

Physics Faculty Scholarship

Robots rely on sensors to provide them with information about their surroundings. However, high-quality sensors can be extremely expensive and cost-prohibitive. Thus many robotic systems must make due with lower-quality sensors. Here we demonstrate via a case study how modeling a sensor can improve its efficacy when employed within a Bayesian inferential framework. As a test bed we employ a robotic arm that is designed to autonomously take its own measurements using an inexpensive LEGO light sensor to estimate the position and radius of a white circle on a black field. The light sensor integrates the light arriving from a …

Mathematical Aspects Of Heisenberg Uncertainty Principle Within Local Fractional Fourier Analysis, Yang Xiaojun

Xiao-Jun Yang

In this paper, we discuss the mathematical aspects of the Heisenberg uncertainty principle within local fractional Fourier analysis. The Schrödinger equation and Heisenberg uncertainty principles are structured within local fractional operators.

Mechanical And Electrical Properties Of Single-Walled Carbon Nanotubes Synthesized By Chemical Vapor Deposition, Yuehai Yang

FIU Electronic Theses and Dissertations

Despite the tremendous application potentials of carbon nanotubes (CNTs) proposed by researchers in the last two decades, efficient experimental techniques and methods are still in need for controllable production of CNTs in large scale, and for conclusive characterizations of their properties in order to apply CNTs in high accuracy engineering. In this dissertation, horizontally well-aligned high quality single-walled carbon nanotubes (SWCNTs) have been successfully synthesized on St-cut quartz substrate by chemical vapor deposition (CVD). Effective radial moduli (E_radial) of these straight SWCNTs have been measured by using well-calibrated tapping mode and contact mode atomic force microscopy (AFM). It …

Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Iii. Tangential Motions Using Astrodrizzle Images, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert

Physics and Astronomy Faculty Publications

We have been able to compare with astrometric precision AstroDrizzle processed images of NGC 6720 (the Ring Nebula) made using two cameras on the Hubble Space Telescope. The time difference of the observations was 12.925 yr. This large time base allowed the determination of tangential velocities of features within this classic planetary nebula. Individual features were measured in [N II] images as were the dark knots seen in silhouette against background nebular [O III] emission. An image magnification and matching technique was also used to test the accuracy of the usual assumption of homologous expansion. We found that homologous …

Ionic Liquid-Functionalized Carbon Nanoparticles-Modified Cathode For Efficiency Enhancement In Polymer Solar Cells, Xiaohong Chen, Jiaxiang Yang, Jiong Lu, Kiran Kumar Manga, Kian Ping Loh, Furong Zhu

Professor ZHU, Fu Rong

The power conversion efficiency (PCE) of regioregular poly(3-hexylthiophene) (P3HT) and {6,6}-phenyl C61-butyric acid methylester (PCBM)-based polymer solar cells was increased using an ionic liquid-functionalized carbon nanoparticles (ILCNs) thin film-modified cathode. The PCE of P3HT:PCBM based-polymer solar cells with a conventional aluminum (Al)-only cathode was increased by 20%–30% when the identical devices were made with an ILCNs-modified Al cathode, but its PCE was 10% lower than that of devices with LiF/Al cathode, measured under AM1.5G illumination of 100 mW/cm2. The ILCN interlayer approach, however, offers practical advantages to LiF in terms of its solution-processability, which is compatible with low cost, large …

Thermodynamic Volumes And Isoperimetric Inequalities For De Sitter Black Holes, Brian P. Dolan, David Kastor, David KubiznˇA´K, Robert B. Mann, Jennie Traschen

David Kastor

We consider the thermodynamics of rotating and charged asymptotically de Sitter black holes. Using Hamiltonian perturbation theory techniques, we derive three different first law relations including variations in the cosmological constant, and associated Smarr formulas that are satisfied by such spacetimes. Each first law introduces a different thermodynamic volume conjugate to the cosmological constant. We examine the relation between these thermodynamic volumes and associated geometric volumes in a number of examples, including Kerr-dS black holes in all dimensions and Kerr-Newman-dS black holes in D=4. We also show that the Chong-Cvetic-Lu-Pope solution of D=5 minimal supergravity, analytically continued to positive cosmological …

Characterization Of Mesoscopic Fluid Films For Applications In Spm Imaging And Fabrication Of Nanostructures On Responsive Materials, Xiaohua Wang

Dissertations and Theses

This dissertation focuses on characterization of the mesoscopic fluid film, testing its behavior in different application scenarios, including its role in near-field scanning probe microscopy imaging, contribution to the phononic mechanism in nanotribology phenomena, utilizing it as a natural environment in the study of carbohydrate-protein interactions, and harnessing it as bridge to transport ions in the fabrication of nanostructures on responsive polymer materials.

Due to their high resolution and versatile applications in a variety of fields, the family of scanning probe microscopy (SPM) has found widespread acceptance as an analytical and fabrication tool. However, the working mechanism of SPM that …