Physics Commons^™

Imaging-Based Parametric Resonance In An Optical Dipole-Atom Trap, S. Balik, A. L. Win, M. D. Havey

Physics Faculty Publications

We report sensitive detection of parametric resonances in a high-density sample of ultracold ⁸⁷Rb atoms confined to a far-off-resonance optical dipole trap. Fluorescence imaging of the expanded ultracold atom cloud after a period of parametric excitation shows significant modification of the atomic spatial distribution and has high sensitivity compared with traditional measurements of parametrically driven trap loss. Using this approach, a significant shift of the parametric resonance frequency is observed and attributed to the anharmonic shape of the dipole trap potential. 2009 The American Physical Society.

Wavelength-Division-Multiplexed Transmission Using Semiconductor Optical Amplifiers And Electronic Impairment Compensation, Xiaoxu Li

Electronic Theses and Dissertations

Over the last decade, rapid growth of broadband services necessitated research aimed at increasing transmission capacity in fiber-optic communication systems. Wavelength division multiplexing (WDM) technology has been widely used in fiber-optic systems to fully utilize fiber transmission bandwidth. Among optical amplifiers for WDM transmission, semiconductor optical amplifier (SOA) is a promising candidate, thanks to its broad bandwidth, compact size, and low cost. In transmission systems using SOAs, due to their large noise figures, high signal launching powers are required to ensure reasonable optical signal-to-noise ratio of the received signals. Hence the SOAs are operated in the saturation region and the …

Nonlinear Femtosecond Near Infrared Laser Structuring In Oxide Glasses, Arnaud Royon

Electronic Theses and Dissertations

Three-dimensional femtosecond laser structuring has a growing interest because of its ease of implementation and the numerous possible applications in the domain of photonic components. Structures such as waveguides, diffraction gratings, optical memories or photonic crystals can be fabricated thanks to this technique. Its use with oxide glasses is promising because of several advantages; they are resistant to flux and ageing, their chemical composition can easily be changed to fit the well-defined requirements of an application. They can already be found in Raman amplifiers, optical fibers, fiber lasers, and other devices. This thesis is based on two axes. The first …

Monoclinic Optical Constants, Birefringence, And Dichroism Of Slanted Titanium Nanocolumns Determined By Generalized Ellipsometry, Daniel Schmidt, Benjamin Booso, Tino Hofmann, Eva Schubert, Andrew Sarangan, Mathias Schubert

Electrical and Computer Engineering Faculty Publications

Generalized spectroscopic ellipsometry determines the principal monoclinic optical constants of thin films consisting of slanted titanium nanocolumns deposited by glancing angle deposition under 85° incidence and tilted from the surface normal by 47°. Form birefringence measured for wavelengths from 500 to 1000 nm renders the Ti nanocolumns monoclinic absorbing crystals with c-axis along the nanocolumns, b-axis parallel to the film interface, and 67.5° monoclinic angle between the aand c-axes. The columnar thin film reveals anomalous optical dispersion, extreme birefringence, strong dichroism, and differs completely from bulk titanium. Characteristic bulk interband transitions are absent in the spectral range investigated.

The Effect Of Realistic Focal Conditions On Strong -Field Double Ionization, Jay Paul Paquette

Dissertations, Theses, and Masters Projects

In recent years, a great deal of progress has been made in understanding the ionization processes that result from the interaction of an intense laser pulse with multielectron atoms. However, due to experimental limitations, the effect of the laser field's spatial dependence on strong-field processes has rarely been investigated. Presented in this work is a theoretical analysis of this spatial dependence including a proposal for an experimentally observable result of the phenomenon. We begin by outlining the elements of the laser field that will vary as a function of position and show their effects on simple free electron trajectories. We …

Holographic Recording In Acrylamide Photopolymers: Thickness Limitations, Mohammad Mahmud, Izabela Naydenova, Nitesh Pandey, Tzvetanka Babeva, Raghavendra Jallapuram, Suzanne Martin, Vincent Toal

Articles

Holographic recording in thick photopolymer layers is important for application in holographic data storage, volume holographic filters and correlators. Here, the characteristics of acrylamidebased photopolymer layers having thickness from 250 μm to 1-mm were studied. For each layer thickness samples with three different values of absorbance were studied. By measuring both the first order diffraction efficiency growth of holographically recorded gratings and studying the diffraction patterns obtained, the influence of scattering on the diffraction efficiency of thick volume holographic gratings was analyzed. It was observed that above a particular thickness and absorbance, the first order diffraction efficiency significantly decreased because …

A Single Beam Data Writing Process For Holographic Data Storage, Suzanne Martin, Denis Bade, Izabela Naydenova, Vincent Toal

Conference Papers

A concept is described that could allow Holographic Data Storage with angular multiplexing using, uniquely, only one data writing beam; pre-recorded ‘seed’ gratings are illuminated with one writing beam in order to produce a data grating.

Out-Of-Plane Vibration Analysis With A Transmission Holographic Optical Element Based Electronic Speckle Pattern Interferometer, Viswanath Bavigadda, Vincent Toal, Raghavendra Jallapuram, Emilia Mihaylova

Conference Papers

A simple electronic speckle pattern interferometer (ESPI) using a transmission holographic optical element (THOE) is presented. The THOE is designed to create a speckled reference beam in the interferometer. It is a transmission hologram of a diffusely transmitting glass plate A specific requirement for the fabrication of the THOEs is for them to be recorded at one wavelength at which the recording material is photosensitive and reconstructed using a near infrared laser diode which can be current modulated for phase shifting purposes. A partially reflective glass plate provides illumination of the object along the normal to its surface, ensuring that …

Ocular Microtremor Laser Speckle Metrology, Mohammed Al-Kalbani, Emilia Mihaylova, Niamh Collins, David Coakley, Gerard Boyle, Vincent Toal

Conference Papers

Ocular Microtremor (OMT) is a continual, high frequency physiological tremor of the eye present in all subjects even when the eye is apparently at rest. OMT causes a peak to peak displacement of around 150nm-2500nm with a broadband frequency spectrum between 30Hz to 120Hz; with a peak at about 83Hz. OMT carries useful clinical information on depth of consciousness and on some neurological disorders. Nearly all quantitative clinical investigations have been based on OMT measurements using an eye contacting piezoelectric probe which has low clinical acceptability. Laser speckle metrology is a candidate for a high resolution, non-contacting, compact, portable OMT …

Optical Patterning Of Photopolymerisable Materials, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal

Conference Papers

Holographic recording is an effective approach for photopolymer surface patterning. It has been previously utilised in acrylamide-based photopolymers and a spatial frequency limit of 200 l/mm has been observed. We report the successful inscription of submicrometer resolution patterns. The spatial frequency response has been extended to 1550 l/mm by introduction of thermal post recording treatment. Initial results from the optical patterning utilising a spatial light modulation (SLM) reveal that the amplitude of the photoinduced surface relief structures is larger in comparison to the amplitude obtained by holographic recording.

Optical Properties Of Charged Polymer With Nano-Sized Zeolite Inclusions, Temenujka Yovcheva, Izabela Naydenova, Ivanka Vlaeva, Rosen Todorov, Vincent Toal, Simeon Sainov

Conference Papers

The optical characteristics of photopolymer films doped with nanoparticles are studied. The investigated systems consist of a soft polymer matrix containing porous zeolite nanoparticles with concentrations varied in the range from 0wt.% to 7wt.%. 40μm thick layers are obtained by casting the photopolymer nanocomposite solution on glass substrates. The corona charging influence on the transmission spectra and on the surface and the effective refractive index of the dry layers is investigated.

Recent And Emerging Applications Of Holographic Photopolymers And Nanocomposites, Izabela Naydenova, Pavani Kotakonda, Raghavendra Jallapuram, Tsvetanka Babeva, Denis Bade, Suzanne Martin, Vincent Toal, Svetlana Mintova

Conference Papers

Sensing applications of holograms may be based on effects such as change in the spacing of the recorded fringes in a holographic diffraction grating in the presence of an analyte so that the direction of the diffracted laser light changes, or, in the case of a white light reflection grating, the wavelength of the diffracted light changes. An example is a reflection grating which swells in the presence of atmospheric moisture to indicate relative humidity by a change is the colour of the diffracted light. These devices make use of the photopolymer’s ability to absorb moisture. In a more versatile …

An Infrared Imaging Method For High-Throughput Combinatorial Investigation Of Hydrogenation-Dehydrogenation And New Phase Formation Of Thin Films, H. Oguchi, Jason R. Hattrick-Simpers, I. Takeuchi, E. J. Heilweil, L. A. Bendersky

Faculty Publications

We have developed an infrared imaging setup enabling in situ infrared images to be acquired, and expanded on capabilities of an infrared imaging as a high-throughput screening technique, determination of a critical thickness of a Pd capping layer which significantly blocks infrared emission from below, enhancement of sensitivity to hydrogenation and dehydrogenation by normalizing raw infrared intensity of a Mg thin film to an inert reference, rapid and systematic screening of hydrogenation and dehydrogenation properties of a Mg–Ni composition spread covered by a thickness gradient Pd capping layer, and detection of formation of a Mg₂Si phase in a …

The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi

Faculty Publications

The effect of the crystallinity and the grain texturing of CoPt hard layers on exchange coupled Fe/CoPt soft/hard magnetic systems was studied using gradient thickness multilayer thin films. We have studied the hard layer structures by transmission electron microscopy and x-ray diffraction, and characterized the exchange coupling interaction through magnetization loops obtained by the magneto-optical Kerr effect measurement. We found that exchange coupling strongly depends on the crystalline characteristics of the CoPt hard layer. There is correlation between the mixture of different grain orientations of the CoPt hard layer and coupling efficiency. In particular, interlayer coupling is enhanced when there …

Comparative Study Of Forward And Diffusely Scattered Light In A Coherently Prepared Ultracold Rubidium Gas, Rocio Gisel Olave Gonzalez

Physics Theses & Dissertations

A comparison between forward and diffusely scattered light propagating in a coherently prepared ultracold ⁸⁷Rb atomic vapor is presented. This research is part of the ongoing effort to characterize the processes, such as diffusion, that contribute to coherence loss in atomic media under conditions of electromagnetically induced transparency, for applications in realistic systems. Toward this end, a magneto optical trap (MOT) of ⁸⁷Rb has been built, and the atomic vapor sample characterized in terms of atomic density, shape and size, temperature, and optical depth. Next, two co-propagating beams were sent through the sample, to establish an electromagnetically induced …

Light Scattering In Ultracold High Density Rubidium Vapor, Salim Balik

Physics Theses & Dissertations

Recent developments in laser cooling and trapping opened the door to a world full of new opportunities for research in atomic, molecular and optical physics as well as condensed matter physics. It became possible to do experiments under conditions that are hard to achieve in condensed matter systems but recently have been observed in atomic systems. Bose Einstein Condensation, the Mott insulator transition, and superfluidity are examples of such achievements. Another considerable interest to both condensed matter and atomic physics is Anderson localization of light. The localization phenomenon is named after P. W. Anderson who suggested the possibility of localization …

Soliton Perturbation Theory For A Higher-Order Hirota Equation, Tim Marchant

Tim Marchant

Solitary wave evolution for a higher order Hirota equation is examined. For the higher order Hirota equation resonance between the solitary waves and linear radiation causes radiation loss. Soliton perturbation theory is used to determine the details of the evolving wave and its tail. An analytical expression for the solitary wave tail is derived and compared to numerical solutions. An excellent comparison between numerical and theoretical solutions is obtained for both right- and left-moving waves. Also, a two-parameter family of higher order asymptotic embedded solitons is identified.

Modulation Analysis Of Boundary Induced Motion Of Optical Solitary Waves In A Nematic Liquid Crystal, Tim Marchant

Tim Marchant

We consider the motion of a solitary wave, a nematicon, in a finite cell filled with a nematic liquid crystal. A modulation theory is developed to describe the boundary-induced bouncing of a nematicon in a one-dimensional cell and it is found to give predictions in very good agreement with numerical solutions. The boundary-induced motion is then considered numerically for a two-dimensional cell and a simple extension of the modulation theory from one to two space dimensions is then made, with good agreement being found with numerical solutions for the nematicon trajectory. The role of nematicon shape and relative position to …

A Perturbation Drbem Model For Weakly Nonlinear Wave Run-Ups Around Islands, Tim Marchant

Tim Marchant

In this paper, the dual reciprocity boundary element method (DRBEM) based on the perturbation method is presented for calculating run-ups of weakly nonlinear long waves scattered by islands. Under the assumption that the incident waves are harmonic, the time-dependent nonlinear Boussinesq equations are transformed into three time-independent linear equations by using the perturbation method, where, besides nonlinearity ε, the dispersion μ2 is also included in the perturbed expansion. The first-order solution η0 is found by using the linear long-wave equations. Then η0 is used in two second-order governing equations related to the dispersion and nonlinearity, respectively. Since no any omission …

Material Damage From Ultrashort Bursts Of Light, Jeremy Gulley

Jeremy R. Gulley

No abstract is currently available.

All-Optical Suppression Of Relativistic Self-Focusing Of Laser Beams In Plasmas, Serguei Y. Kalmykov, Sunghwan A. Yi, Gennady Shvets

Serge Youri Kalmykov

It is demonstrated that a catastrophic relativistic self-focusing (RSF) of a high-power laser pulse can be prevented all-optically by a second, much weaker, copropagating pulse. RSF suppression occurs when the difference frequency of the pulses slightly exceeds the electron plasma frequency. The mutual defocusing is caused by the three-dimensional electron density perturbation driven by the laser beat wave slightly above the plasma resonance. A bi-envelope model describing the early stage of the mutual defocusing is derived and analyzed. Later stages, characterized by the presence of a strong electromagnetic cascade, are investigated numerically. Stable propagation of the laser pulse with weakly …

Plurality Of Principal Angles For A Given Pseudo-Brewster Angle When Polarized Light Is Reflected At A Dielectric-Conductor Interface, R. M.A. Azzam, A. Alsamman

Electrical Engineering Faculty Publications

The pseudo-Brewster angle ϕpB of minimum reflectance for p-polarized light and the principal angle ϕ¯ at which incident linearly polarized light of the proper azimuth is reflected circularly polarized are considered as functions of the complex relative dielectric function ε of a dielectric–conductor interface over the entire complex ε plane. In particular, the spread of ϕ¯for a given ϕpB is determined, and the maximum difference (ϕ¯−ϕpB)max is obtained as a function of ϕpB . The maximum difference (ϕ¯−ϕpB)max approaches 45° and 0 in the limit as ϕpB→0 and 90°, respectively. ForϕpB<22.666° , multiple principal angles ϕ¯i , i=1,2,3 , appear for each ε in a subdomain of fractional optical constants. …

Controlling The Transmitted Field Into A Cylindrical Cloak's Hidden Region, Jeffrey S. Mcguirk, Peter J. Collins

Faculty Publications

Constitutive parameters for simplified cylindrical cloaks have been developed such that ε_zµ_θ and ε_zµ_r match those of the ideal cylindrical cloak. Although they are not perfect, simplified cylindrical cloaks have been shown to inherit many of the power-bending properties of the ideal cloak. However, energy is transmitted into simplified cloaks' hidden regions. Here, we develop a constraint equation that can be used to determine how closely field behavior within the simplified cylindrical cloak matches that of the ideal cloak. The deviation from this controlling equation can be reduced by controlling the cloak's parameter value, …

Homogeneous Dbd In N2: 1) Lif, Talif And Electrical Measurements, N. Gherardi, Et. Es-Sebbar, C. Sarra-Bourret, N. Naudé, F. Massines

Dr. Et-touhami Es-sebbar

In this paper we compare two different discharges that can be obtained in a DBD configuration, that is to say the filamentary discharge (usual regime in atmospheric DBD) with the Atmospheric Pressure Townsend Discharge (APTD), which is a homogeneous regime obtained in nitrogen atmosphere. The aim is to help in the understanding of the processes which control the transition from one regime to the other. To do so, the discharge is characterized through electrical measurements, coupled with optical diagnostics among which Laser Induced Fluorescence (LIF) for radical density measurements. The influence of the addition of small quantities of additives on …

Active Species Generation Of Homogeneous Dbd In N2: Experiment And Modelling, N. Gherardi, Et. Es-Sebbar, C. Sarra-Bourret, N. Naudé, F. Massines, D. Tzyganov, P. Ségur, S. Pancheshnyi

Dr. Et-touhami Es-sebbar

No abstract provided.

Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema

Theses and Dissertations

A self-referencing interferometer based closed-loop adaptive optics controller is developed which is designed to operate effectively under strong turbulence conditions. The aberrated optical field is modeled stochastically and then estimates of the state of the system are developed using a steady-state, fixed-gain Kalman filter. The phase of the optical field is considered the state of the system which is wrapped in a limited range of (-π, π]. This phase is unwrapped through the use of a least-squares reconstructor which has been modified to work effectively in the presence of branch points associated with strong turbulence. The conjugate of the optical …

Inhibition Of Linear Absorption In Opaque Materials Using Phase-Locked Harmonic Generation, Marco Centini, Vito Roppo, Eugenio Fazio, Federico Pettazzi, Concita Sibilia, Joseph W. Haus, John V. Foreman, Neset Akozbek, Mark J. Bloemer, Michael Scalora

Electrical and Computer Engineering Faculty Publications

We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second- and third-harmonic generation in strongly absorbing materials, GaAs, in particular, at frequencies above the absorption edge.

A 100-fs pump pulse tuned to 1300 nm generates 650 and 435 nm second- and third-harmonic pulses that propagate across a 450−μm-thick GaAs substrate without being absorbed.

We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress on them its dispersive properties.

Stimulated Brillouin Scattering Phase Conjugation In Fiber Optic Waveguides, Steven M. Massey

Theses and Dissertations

The objective of this research effort was to demonstrate the path to continuous wave, coherent beam combination through stimulated Brillouin scattering phase conjugation in optical fiber. This work experimentally determined the fiber parameters necessary for phase conjugation in step-index optical fiber. Continuous wave phase conjugation using stimulated Brillouin scattering in step-index fibers was achieved for the first time with a fidelity of 0.8 and a threshold power of 16 W in a 15-m fiber with 0.13 NA. A fidelity of 0.8 was also achieved using 40 m of fiber with 0.06-NA and a threshold power of 15 W. The fidelity …

Stimulated Brillouin Scattering Continuous Wave Phase Conjugation In Step-Index Fiber Optics, Steven M. Massey, Justin B. Spring, Timothy H. Russell

Faculty Publications

Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length. A phase conjugate fidelity over 80% was measured from SBS in a 40 m fiber using a pinhole technique. Fidelity decreases with fiber length, and a fiber with a numerical aperture (NA) of 0.06 was found to generate good phase conjugation fidelity over longer lengths than a fiber with 0.13 NA. Modeling and experiment support previous work showing the maximum interaction length which yields a high fidelity phase conjugate beam is inversely proportional to the fiber …

Surface Ion-Electron Recombination As The Main Source Of Atoms In Flowing N2 Dbd, D. Tsyganov, Et. Es-Sebbar, S. Pancheshnyi, N. Gherardi, P. Ségur, F. Massines

Dr. Et-touhami Es-sebbar

No abstract provided.