UAH Physics

Colloquium: 27 October 2009, 2:30pm, OB 234

Thu, 22 Oct 2009 09:54:40 -0500

Coherent nanophotoics: How to subdue optics of metallic nanoparticles via semiconductor quantum dots

One of the main reasons that currently noble metallic nanoparticles are at the center of significant attentions is the fact that they support surface plasmon resonances. These resonances are now the cornerstones of many applications, ranging from optical nanosensors, sub-wavelength optical waveguides, and nano-thermometers, to fundamental physics such as plasmonic control of emission of semiconductor nanostructures. Despite these, control of the optical properties of metallic nanoparticles is still rather an obscure field of research. This is mostly related to the ultra short relaxation times of plasmons, which make any attempt to control optics of metallic nanoparticles face significant challenges.

In this talk, I will review a novel technique that we have recently developed to optically control plasmons in metallic nanoparticles. This technique allows us to use a semiconductor quantum dot as a tool to make a metallic nanoparticle virtually transparent at the peak of its plasmonic absorption. This control of plasmons here requires interaction of a hybrid system consisting of a metallic nanoparticle and a quantum dot with an infrared laser. I will discuss how this process can be used to optically control heat dissipation rate in metallic nanoparticles, forming what we called “thermal electromagnetically induced transparency”.

Seyed Sadedhi
UAHuntsville, Department of Physics

Colloquium: 20 October 2009, 2:30pm, OB 234

Tue, 20 Oct 2009 11:49:24 -0500

Simulation of relativistic shocks and associated radiation from turbulent magnetic fields

Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron–positron jet propagating into an unmagnetized electron–positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electron's transverse deflection behind the shock. The ``jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. New spectra based on simulations will be presented.

Ken Nishikawa
NASA MSFC

Colloquium: 13 October 2009, 2:30pm, OB 234

Mon, 12 Oct 2009 13:59:53 -0500

Termination Shock Surfing

Voyager Observations of the heliospheric termination shock (TS) are presented along with a brief discussion of the current and past state of our knowledge of the heliospheric boundary region formed by the interaction of the Sun's solar wind with the local interstellar medium. Voyager 2 observations of the TS are used to construct a model which indicates that shock surfing can account for the 'missing' energy in the solar wind plasma downstream of the TS. (Time permitting) I will discuss our new idea for using the conservation laws for macroscopic conducting fluids (i.e. the conservation laws underlying MHD) to include the back-reaction of the shock surfing mechanism on the electromagnetic fields in a quasi-self-consistent fashion.
Ross Burrows
UAHuntsville

Colloquium: 6 October 2009, 2:30pm, OB 234

Mon, 05 Oct 2009 15:01:04 -0500

Interferometer as an Imaging System

The primary function of an interferometer is to produce a set of rays normal to the ideal test surface. This is often aided by the presence of a null lens for aspheric mirrors. However, there is an important secondary function...imaging. In commercial systems there is always a control for imaging the test optic’s aperture. In laboratory practice what’s usually done is to simply obtain a sharp image of the mirror rim/edge. But we should ask ourselves how well an interferometer performs this imaging function. Are the design criteria between the two functions really compatible? In this presentation we provide an initial look into this question. We will do so in the context of the Fizeau interferometer since this type is currently the main industry workhorse. The test optic employed will be a parabolic mirror and also an off-axis component of that mirror, i.e. an OAP. A null lens will connect the aspheres to the Fizeau. Our chief investigative tool will be optical modeling. The code employed is Zemax. Joe Geary
UAHuntsville CAO

Colloquium: 29 September 2009, 2:30pm, OB 234

Wed, 23 Sep 2009 14:31:04 -0500

The Legacy of the Ulysses Mission

Steve Suess
NASA MSFC

Special Seminar: 12 October 2009, 2:30pm, OB 234

Wed, 23 Sep 2009 14:22:05 -0500

Mathematica in the Classroom

Aaron Pollock
Wolfram Research

MS Thesis Defense: 7 October 2009, 8:30am, OB 234

Wed, 23 Sep 2009 14:19:34 -0500

Using Saturated Absorption Spectroscopy for Detuned Laser Locking

Mr. Charles "Shampoo" Schambeau
Department of Physics

Colloquium: 22 September 2009, 2:30pm, OB 234

Tue, 15 Sep 2009 10:13:52 -0500

The Acceleration of Charged Particles at Collisionless Shocks in Space and Astrophysics

The acceleration of charged particles to the highest energies ever measured (~10**20 eV ) occurs in Astrophysical settings. How this happen is still not fully understood. It is believed by many that the diffusive shock acceleration mechanisms is the key to this puzzle because it naturally produces a power law for the accelerated charged particle spectrum over a wide range of energies as observations show. However, radiation measurements from remote astrophysical shocks such as supernovae remnants can take us only so far in figuring out the details of shock acceleration since the radiation is produced by the shock accelerated particles and we do not see these particles directly. With the discovery of the termination shock around the Sun in the solar system plasma when the Voyager 1 and 2 space craft crossed it in 2004 and 2007, we have detailed direct measurements of charged particles accelerated by a large-scale collisionless shock and about the shock itself. We will discuss how the Voyager observations challenge us to come up with a more sophisticated model for charged particle shock acceleration at quasi-perpendicular shocks, which in some ways are not as well understood as at quasi-parallel shocks.

Jakobus A. le Roux, Dept. of Physics
UAHuntsville

Colloquium: 15 September 2009, 2:30pm, OB 234

Wed, 09 Sep 2009 10:28:46 -0500

Electron Kinetics in Gas Discharges

Gas discharges present an example of extremely non-equilibrium systems. This property comes from a large difference between the mass of electrons and the mass of atoms and molecules. Due to the great distinction of mass, the energy exchange in elastic collisions between electrons and gas molecules is inefficient, and the application of electric fields results in electron heating up to energies of a few eV (30,000K) comparable to ionization potential of atoms (with gas remaining at the room temperature). Low temperature plasmas (LTP) of gas discharges are characterized by low ionization degree of 10-6-10-3 and electron temperatures two orders of magnitude larger than gas temperatures. The electrons produce exotic chemical reactions not possible in equilibrium systems. These LTPs are widely used in many modern technologies including semiconductor manufacturing (etching and deposition of computer chips), lighting, plasma display panels, etc. We will present examples of electron kinetics in different plasma sources, describe intriguing physics of self-organization at the kinetic level for ionization waves (striations) in Direct Current discharges, and describe state-of-the-art modeling and simulation of electron kinetics in LTPs.

Dr. Vladimir Kolobov
UAHuntsville

Colloquium: 8 September 2009, 2:30pm, OB 234

Thu, 03 Sep 2009 14:20:42 -0500

Sun-Earth Connection: A Tale of Two Ends from a Personal Perspective

Our Sun, as a variable star, plays a dominant role in controlling the near-Earth space environment. It is constantly emitting highly ionized material mostly composed of protons and electrons (so-called "solar wind"), carrying solar magnetic field. Thus formed solar atmosphere, called corona, stretches all the way to the Earth and beyond. Its dynamic and magnetic interactions with near-Earth space generate various adverse effects, ranging from spacecraft malfunction in space to power outage on the ground, impacting various aspects of human activities. I will briefly describe such effects related to the emerging research area of space weather. Then I will report my contributions to this area on two topics. One is the extrapolation of the solar coronal magnetic field from magnetic field observations on the solar surface, especially that in a finite active region. The other is the quantitative characterization, from in-situ spacecraft data, of transient structures ejected from the Sun that are often responsible for causing disturbances in near-Earth environment. The effort of seeking physical and causal connections between the Sun and Earth will also be presented. Finally I will summarize and offer some outlook for future endeavors, especially in the context of further collaborations with solar physicists and support by observational facilities, within CSPAR.

Qiang Hu
UAHuntsville

Colloquium: 1 September 2009, 2:30pm, OB 234

Thu, 03 Sep 2009 14:19:46 -0500

Effects of an Intracavity Resonant Medium on an Optical Cavity

Optical cavities provide sensitive detection of rotation through the shift in the cavity resonance frequencies, resulting from the Sagnac effect. We investigated the use of the anomalous dispersion, asscioated with an absorption resonance from an intracavity medium, for increasing the frequency separation of the cavity modes. Using a simple Fabry-Perot resonator with an intracavity rubidium vapor cell, we experimentally demonstrated the increase in the cavity scale factor, and found it to be in good agreement with theory for our absorption resonance, with small deviations resulting from the multi-level nature of the Rb87 D2 transition. The widths of the cavity resonances, modified by the presence of the dispersive medium, did not grow as quickly as the scale factor, resulting in increased cavity sensitivity, a finding contrary to previous expectations. We also demonstrated that the ground state hyperfine structure of the Rb87 atom can be used to tune the cavity scale factor via the technique of optical hyperfine pumping.

Krishna Myneni
US Army RDECOM

Colloquium: 25 August 2009, 2:30pm, OB 234

Tue, 18 Aug 2009 14:36:57 -0500

The Structure of the Outer Heliosphere: Numerical Simulations vs. Spacecraft Observations

The outer heliosphere is the part of the solar wind (SW) which is determined by its interaction with the local interstellar medium (LISM). Since the LISM is partially ionized, charge exchange between atoms and ions plays a major role in the SW-LISM interaction. The topology of this interaction will be described as a function of the SW and LISM properties. The coupling of the interstellar and interplanetary magnetic fields (IMF and ISMF) at the heliospheric interface will be described. The importance of pick-up ions will be emphasized.

Several examples of numerical solution of the SW-LISM interaction problem will be given in the attempt to match them the observations performed by the Voyager 1 (V1) and Voyager 2 (V2) spacecraft. The combined effect of charge exchange and ISMF pressure on the heliospheric asymmetries will be analyzed. Observational constraints on the ISMF orientation will be addressed. I will also show the interaction of the heliospheric discontinuities with the SW perturbations. Special attention will be given to the heliospheric response to Sun’s rotation and 11-year period of solar activity.

Finally, I will describe a suite of numerical codes developed by our research group in CSPAR/Physics Department. This suite is capable of performing rather sophisticated, very high-resolution calculations of a variety of problems in space physics.

Nikolai V. Pogorelov
UAHuntsville

NASA Student Ambassador

Thu, 28 May 2009 09:19:39 -0500

Ms. Laura Seward, graduate student in the Department of Physics, has been selected to be among the first group of NASA Student Ambassadors.

Colloquium: 14 April 2009, 2:30pm, OB 234

Tue, 14 Apr 2009 08:07:45 -0500

Whister Wave Turbulence in Space Plasmas

Dastgeer Shaikh, UAHuntsville

Colloquium: 21 April 2009, 2:30pm, OB 234

Wed, 01 Apr 2009 11:07:17 -0500

Design and Optimization of Nanostructured Optical Filters

Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or complicated conversions between optical and electrical signals.

This research explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths.

While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs.

Jeremiah Brown
Grassmere Dynamics

Colloquium: 31 March 2009, 2:30pm, OB 234

Mon, 30 Mar 2009 11:02:10 -0500

Infrared Sources for Dynamic Radiometric Sensor Testing

The presentation will explore some of the challenges and performance issues encountered when using infrared semiconductor lasers and LEDs for dynamic radiometric sensor testing. A hybrid projection system combining the technologies of an emissive resistor array device and an optically scanned laser diode array projector (LDAP) will be discussed first. It will be shown that high apparent temperature (high radiance) simulations can most efficiently be produced by the luminescent infrared radiation emitted by semiconductor sources. Aspects of the ideal infrared source will be described along with research to develop new devices to fill these technology gaps in dynamic infrared sensor testing.

Dr. Tommy Cantey
AMRDEC

Outstanding GRA

Tue, 24 Mar 2009 08:55:52 -0500

Ms. Nicole Hasler has been awarded an Outstanding Graduate Research Assistant Award from the College of Science for the 08-09 AY. Ms. Hasler works with Prof. Bonamente.

Special Seminar: 3 April 2009, 2:30pm, OB 234

Mon, 23 Mar 2009 11:36:41 -0500

Morphology and dynamics of polymer nanocomposites

Dr. M Goswami, ORNL

Colloquium: 24 March 2009, 2:30pm, OB 234

Mon, 23 Mar 2009 11:33:57 -0500

Fermi GBM Observations of Terrestrial Gamma Flashes

Dr. Michael Briggs
UAHuntsville

Turbulence Simulation

Tue, 03 Mar 2009 08:35:47 -0600

Assistant Professor Dastgeer Shaikh, using a new 3D simulation of turbulence cascading, has solved a physics mystery first observed in the solar wind 15 years ago.

Colloquium: 10 March 2009, 2:30pm, OB 234

Tue, 03 Mar 2009 08:28:09 -0600

RY Scuting Along: Studying a Messy Binary

A long time ago in a binary far, far away, one star was growing while another was shrinking. Even though this actually happened 6000 years ago, the light from these events in the RY Scuti binary is just getting to us. Right now we see one star dumping some of its mass onto its companion - active mass transfer and a messy transfer at that. I'll show you how we gleaned information about the two stars (such as masses) and determined that there is a 2000 A.U. double-ring nebula and a 1 A.U. circumbinary disk around the two stars, gas leaking from L2, and an accretion torus around the mass gainer. Eventually, one or both of these stars will go supernova.

Erika Grundstrom, Vanderbilt University

Colloquium: 3 March 2009, 2:30pm, OB 234

Tue, 03 Mar 2009 08:25:21 -0600

Characterizing the X-ray emitting plasmas in young stars

Young, low-mass stars are copious producers of X-ray emission indicative of magnetic activity in the plasmas of these stars. The trends seen in correlating X-ray parameters with stellar properties in main sequence stars do not follow for young stars. As a result, different physical mechanisms maybe driving the X-ray emission in young stars. I will present both imaging and spectroscopic data from the Chandra X-ray Observatory of various types of young stars at different evolutionary stages. Our results indicate unique characteristics of the X-ray emitting plasmas of these young stars.
S. Shukla, Vanderbilt University

PlayStation 3 Research

Tue, 24 Feb 2009 10:12:38 -0600

How did Sony's PlayStation 3 (or, actually, sixteen of them) help Assitant Professor Lior Burko solve a fundamental astrophysics question? Click on the link to find out.

NSF CAREER Award

Tue, 24 Feb 2009 10:08:33 -0600

Dr. Gang Li, Assistant Professor of Physics, has been awarded a prestigious CAREER award from the National Science Foundation.

Record Gamma-Ray Burst

Fri, 20 Feb 2009 09:01:11 -0600

Physics graduate student Adam Goldstein's first day on the job tending the Gamma-ray Burst Monitor (GBM) on NASA's Fermi Gamma-ray Space Telescope was a doozy. Goldstein was still learning the ropes the evening of 16 September 2008, nearing the end of his 12-hour on-call shift, when the GBM called his cell phone to signal that a burst had been detected. And what a burst...

PhD Dissertation Defense: 11 March 2009, 10:00am, OB 234

Wed, 18 Feb 2009 10:22:40 -0600

Detection of Spatially Extended Sources in High Energy Astrophysics with Special Application to Lunar Occultation

Occultation is a technique that enables image reconstruction and source identification with a non-imaging detector. Such an approach is well suited for a future survey mission in nuclear astrophysics. In particular, the Lunar Occultation Technique (LOT) utilizes the Moon as an occulting object and is the basis of a new gamma-ray survey mission concept, the Lunar OCcultation Observer (LOCO). Techniques utilizing the LOT to detect spatially extended emission, such as emission from the Galactic plane or Galactic Center region, have been developed. Using knowledge of detector position in lunar orbit, combined with lunar ephemeris and relevant coordinate transformations, occultation time series can be used to reconstruct skymaps of these extended Galactic emissions. Monte-Carlo Markov Chains (MCMC), incorporating the Metropolis-Hastings algorithm for parametric model testing, form the basis of the technique. Performance of the imaging methodology, and its application to nuclear astrophysics will be presented.

Mr. Peter Jenke

Alabama Academy of Science

Thu, 22 Jan 2009 10:55:31 -0600

The annual meeting of the Alabama Academy of Science will occur 26-27 March 2009 on the beautiful campus of the University of West Alabama. Faculty and students are encouraged to consider presenting a paper or poster at this meeting.

New Course

Mon, 17 Nov 2008 08:58:54 -0600

for Spring 2009: PH 615, Introduction to Radiological Physics. The first course in a planned MS curriculum in Medical Physics. Instructor: Dr. Rob Rice, Board Certified, American Board or Radiology.

USRA 2008 Scholarship

Tue, 23 Sep 2008 12:57:02 -0500

Ms. Ashley Campbell, a senior Physics and Mathematics major was awarded the John R. Sevier Memorial Scholarship by The Universities Space Research Association. USRA's selection committee chose an outstanding group of four students in physical science and engineering disciplines from colleges across the US.

Distinguished Professor

Mon, 30 Jun 2008 13:35:31 -0500

Dr. Richard Lieu has been named Distinguished Professor by the University of Alabama Board of Trustees at their June meeting.

Goldwater Scholar

Mon, 31 Mar 2008 13:58:52 -0500

Physics major Danielle Nuding has just been awarded a prestigious Goldwater Scholarship! Ms. Nuding is a physics major specializing in atmospheric science.

U.S. News & World Report Ranking

Mon, 31 Mar 2008 13:56:07 -0500

places the UAH Department of Physics in the top 100 graduate programs in physics nationwide. Click on the link to see the list or search for other programs.

Outstanding GTA

Mon, 24 Mar 2008 09:05:59 -0500

Stanford El-Nemr has been awarded the College of Science Outstanding Graduate Teaching Assistant Award for the 07-08 AY.

Chan Chair of Physics

Thu, 14 Feb 2008 09:04:04 -0600

Gary Zank is the next Pei-Ling Chan Chair of Physics, and this marks the beginning of a major expansion of the Department in the area of space physics. Six additional tenure-track positions will be filled in the next academic year. Dr. Zank will also serve as CSPAR Director, and comes to UAH at the end of this semester.

AGU Outstanding Student Paper

Mon, 04 Feb 2008 10:31:43 -0600

Graduate student Phillip Bitzer received the Outstanding Student Paper Award for his presentation at the 2007 American Geophysical Union (AGU) Fall Meeting in San Francisco. His paper on atmospheric lightening was recognized as among the best of a strong group of student presenters.

Judy Franz Honored for Physics Education Work

Mon, 10 Dec 2007 12:27:03 -0600

Dr. Judy Franz, Professor of Physics and executive officer of the American Physical Society (APS), will receive the Melba Newell Phillips Medal from the American Association of Physics Teachers (AAPT) in recognition of her creative leadership and dedicated service to science education. It will be presented at the AAPT winter meeting in Baltimore.

Big Piece of Universe Missing

Tue, 06 Nov 2007 12:27:33 -0600

New calculations might leave the mass of the universe as much as 10 to 20 percent lighter than previously calculated.