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2005

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Full-Text Articles in Physics

Afci Quarterly Input – Unlv October 1 Through December 31, 2005, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division Dec 2005

Afci Quarterly Input – Unlv October 1 Through December 31, 2005, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.


High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee Dec 2005

High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee

Faculty Publications

We have demonstrated a high-temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual-chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high-temperature vacuum valves and glass-to-metal seals. We have observed over 50% absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2µW/cm2 saturation intensity of the unbroadened transition. The techniques presented ...


Stressed Liquid-Crystal Optical Phased Array For Fast Tip-Tilt Wavefront Correction, Bin Wang, Guoqiang Zhang, Anatoliy Glushchenko, John West, Philip Bos, Paul Mcmanamon Dec 2005

Stressed Liquid-Crystal Optical Phased Array For Fast Tip-Tilt Wavefront Correction, Bin Wang, Guoqiang Zhang, Anatoliy Glushchenko, John West, Philip Bos, Paul Mcmanamon

John L West

A liquid-crystal optical phased-array technology that uses stressed liquid crystals provides a new type of tip-tilt wavefront corrector. It demonstrates a very fast time response (10 kHz) and high beam-steering efficiency (similar to 91%). The new technology presented here will allow for a nonmechanical, high-speed correction with simple device construction.


Stressed Liquid-Crystal Optical Phased Array For Fast Tip-Tilt Wavefront Correction, Bin Wang, Guoqiang Zhang, Anatoliy Glushchenko, John L. West, Philip Bos, Paul F. Mcmanamon Dec 2005

Stressed Liquid-Crystal Optical Phased Array For Fast Tip-Tilt Wavefront Correction, Bin Wang, Guoqiang Zhang, Anatoliy Glushchenko, John L. West, Philip Bos, Paul F. Mcmanamon

Philip J. Bos

A liquid-crystal optical phased-array technology that uses stressed liquid crystals provides a new type of tip-tilt wavefront corrector. It demonstrates a very fast time response (10 kHz) and high beam-steering efficiency (similar to 91%). The new technology presented here will allow for a nonmechanical, high-speed correction with simple device construction.


Nonmetal Ordering In Tic1-Xnx: Ground-State Structure And The Effects Of Finite Temperature, Gus L. W. Hart, Brian Kolb Dec 2005

Nonmetal Ordering In Tic1-Xnx: Ground-State Structure And The Effects Of Finite Temperature, Gus L. W. Hart, Brian Kolb

Faculty Publications

The TiC1-xNx system has long been prized in industry because of its desirable thermodynamic and hardness characteristics. Previous studies have not produced comprehensive results describing the ordering tendencies of TiC1-xNx at any temperature. We apply the mixed-basis cluster expansion and Monte Carlo methods to the problem and find a fascinating array of ground-state structures occurring at precise nitrogen-concentration intervals of ∆x=1/16 and related to each other by simple (201) quasisuperlattice motifs. Thermodynamic Monte Carlo results indicate that the critical ordering temperatures at all concentrations are well below room temperature. short-range ordering develops at T ≈ 800 K and exhibits ...


Magnetic And Spectroscopic Characteristics Of Znmno System, Aswini K. Pradhan, D. Hunter, Kai Zhang, J.B. Dadson, S. Mohanty, T.M. Williams, K. Lord, R.R. Rakimhov, U.N. Roy, Y. Cui, A. Burger, Jun Zhang, David J. Sellmyer Dec 2005

Magnetic And Spectroscopic Characteristics Of Znmno System, Aswini K. Pradhan, D. Hunter, Kai Zhang, J.B. Dadson, S. Mohanty, T.M. Williams, K. Lord, R.R. Rakimhov, U.N. Roy, Y. Cui, A. Burger, Jun Zhang, David J. Sellmyer

David Sellmyer Publications

We report on the observation of room-temperature ferromagnetism in epitaxial (Zn,Mn)O films grown by a pulsed-laser deposition technique using high-density targets. The X-ray, microscopic, spectroscopic and magnetic properties of target material containing 6 at.% of Mn and films were compared. The target shows the presence of large clusters exhibiting paramagnetic behavior. However, ferromagnetic properties were observed in (Zn,Mn)O films grown at a substrate temperature of 500 °C and with an oxygen partial pressure of 1 mTorr. Although, crystalline quality of the film improves with increasing substrate temperature, the ferromagnetism becomes weaker.


Electromagnetism In Gravitational Collapse, Craig Ernest Skinfill Dec 2005

Electromagnetism In Gravitational Collapse, Craig Ernest Skinfill

Theses and Dissertations

A numerical approach to including electromagnetism with general relativity is developed using GRAXI as a starting point. We develop a mathematical model describing electromagnetism coupled to a scalar field in an evolving axisymmetric spacetime. As there are numerous formulations of electromagnetism, we evalute different formulations in a limited flat space case. The full curved space system is then developed, using the flat case as a guide to implementing electromagnetism. This model is then implemented using GRAXI as a code base.


An Event-Based Approach To Validating Solar Wind Speed Predictions: High-Speed Enhancements In The Wang-Sheeley-Arge Model, M. J. Owens, C. N. Arge, Harlan E. Spence, A. Pembroke Dec 2005

An Event-Based Approach To Validating Solar Wind Speed Predictions: High-Speed Enhancements In The Wang-Sheeley-Arge Model, M. J. Owens, C. N. Arge, Harlan E. Spence, A. Pembroke

Physics Scholarship

[1] One of the primary goals of the Center for Integrated Space Weather Modeling (CISM) effort is to assess and improve prediction of the solar wind conditions in near-Earth space, arising from both quasi-steady and transient structures. We compare 8 years of L1 in situ observations to predictions of the solar wind speed made by the Wang-Sheeley-Arge (WSA) empirical model. The mean-square error (MSE) between the observed and model predictions is used to reach a number of useful conclusions: there is no systematic lag in the WSA predictions, the MSE is found to be highest at solar minimum and lowest ...


Laser-Controlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi Dec 2005

Laser-Controlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We analyze theoretically the dynamics of N electrons localized in a narrow semiconductor quantum ring under a train of phase-locked infrared laser pulses. The pulse sequence is designed to control the total angular momentum of the electrons. The quantum ring can be put in states characterized by strong currents. The local magnetic field created by these currents can be used for a selective quantum control of single spins in semiconductor systems. The current generation in quantum rings with finite width is also studied.


Spin-Photovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi Dec 2005

Spin-Photovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We consider the current induced in a quantum wire by external electromagnetic radiation. The photocurrent is caused by the interplay of spin-orbit interaction (Rashba and Dresselhaus terms) and an external in-plane magnetic field. We calculate this current using a Wigner functions approach, taking into account radiation-induced transitions between transverse subbands. The magnitude and the direction of the current depends on the Dresselhaus and Rashba constants, strength of magnetic field, radiation frequency, and intensity. The current can be controlled by changing some of these parameters.


Rescattering Effects In The Multiphoton Regime, M. V. Frolov, A. V. Flegel, N. L. Manakov, Anthony F. Starace Dec 2005

Rescattering Effects In The Multiphoton Regime, M. V. Frolov, A. V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

LETTER TO THE EDITOR

The plateau features that characterize the low-frequency spectra of fundamental strong-field processes such as harmonic generation, above-threshold ionization and laser-assisted electron-atom scattering are shown to exist also for photon energies Eγ of the order of the energy |E0| of a bound electron. The existence of these rescattering effects in such a high-frequency (and thus nontunnelling) regime is supported by accurate quantum analyses of intense Ti-Sapphire laser interactions with halogen negative ions, for which Eγ ≈ 0.5|E0|.


Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson Dec 2005

Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson

Faculty Publications

An isothermal model of ultracold neutral plasma expansion is extended to systems without spherical symmetry. It is used to interpret new fluorescence measurements on ultracold neutral calcium plasmas. For a self-similar expansion, the fluid equations are solved both analytically and numerically. The density and velocity solutions are used to predict fluorescence signals induced by a laser beam weakly focused into the plasma. Despite the simplicity of the model, predicted fluorescence signals reproduce major features of the experimental data


Structural Studies On A Mitochondrial Glyoxalase Ii, Gishanthi P. K. Marasinghe, Ian M. Sander, Brian Bennett, Gopal R. Periyannan, Ke-Wu Yang, Christopher A. Makaroff, Michael W. Crowder Dec 2005

Structural Studies On A Mitochondrial Glyoxalase Ii, Gishanthi P. K. Marasinghe, Ian M. Sander, Brian Bennett, Gopal R. Periyannan, Ke-Wu Yang, Christopher A. Makaroff, Michael W. Crowder

Physics Faculty Research and Publications

Glyoxalase 2 is a β-lactamase fold-containing enzyme that appears to be involved with cellular chemical detoxification. Although the cytoplasmic isozyme has been characterized from several organisms, essentially nothing is known about the mitochondrial proteins. As a first step in understanding the structure and function of mitochondrial glyoxalase 2 enzymes, a mitochondrial isozyme (GLX2-5) from Arabidopsis thaliana was cloned, overexpressed, purified, and characterized using metal analyses, EPR and 1H NMR spectroscopies, and x-ray crystallography. The recombinant enzyme was shown to bind 1.04 ± 0.15 eq of iron and 1.31 ± 0.05 eq of Zn(II) and to exhibit ...


Fluid And Kinetic Structure Of Magnetic Merging In The Swarthmore Spheromak Experiment, W. H. Matthaeus, C. D. Cothran, Matthew Joseph Landreman , '03, Michael R. Brown Dec 2005

Fluid And Kinetic Structure Of Magnetic Merging In The Swarthmore Spheromak Experiment, W. H. Matthaeus, C. D. Cothran, Matthew Joseph Landreman , '03, Michael R. Brown

Physics & Astronomy Faculty Works

Measurement of the in-plane Lorentz force and the out-of-plane magnetic field associated with the Hall electric field near the reconnection zone in the Swarthmore Spheromak Experiment (SSX) confirms expectations, based on simulation, theory and spacecraft data, that the quadrupolar out-of-plane magnetic field is a signature of collisionless effects in magnetic reconnection with a weak guide field.


Multiple Channel Laser Beam Combination And Phasing Using Stimulated Brillouin Scattering In Optical Fibers, Brent W. Grime Dec 2005

Multiple Channel Laser Beam Combination And Phasing Using Stimulated Brillouin Scattering In Optical Fibers, Brent W. Grime

Theses and Dissertations

Brightness scaling lasers using stimulated Brillouin scattering (SBS) in optical fibers is explored. A multiple-channel amplifier approach is used to increase the total power of a laser system while avoiding a significant burden on a single channel. The work explores two approaches utilizing both SBS beam cleanup and SBS piston error conjugation. A unique beam combiner that takes advantage of the SBS beam cleanup properties of a long, gradient-index multimode fiber was designed and tested. The beam combiner was developed to combine multiple-channel laser beams simultaneously with high input and output coupling efficiency. The design for the SBS beam combiner ...


Dynamical Control Of Qubit Coherence: Random Versus Deterministic Schemes, Lea F. Santos, Lorenza Viola Dec 2005

Dynamical Control Of Qubit Coherence: Random Versus Deterministic Schemes, Lea F. Santos, Lorenza Viola

Dartmouth Scholarship

We reexamine the problem of switching off unwanted phase evolution and decoherence in a single two-state quantum system in the light of recent results on random dynamical decoupling methods [L. Viola and E. Knill, Phys. Rev. Lett. 94, 060502 (2005)]. A systematic comparison with standard cyclic decoupling is effected for a variety of dynamical regimes, including the case of both semiclassical and fully quantum decoherence models. In particular, exact analytical expressions are derived for randomized control of decoherence from a bosonic environment. We investigate quantitatively control protocols based on purely deterministic, purely random, as well as hybrid design, and identify ...


Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross Dec 2005

Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross

John Donoghue

We discuss the calculation of the strange magnetic radius of the proton in chiral perturbation theory. In particular we investigate the low energy component of the loop integrals involving kaons. We separate the chiral calculation into a low energy part and a high energy component through use of a momentum space separation scale. This separation shows that most of the chiral calculation comes from high energies where the effective field theory treatment is not valid. The resulting low energy prediction is in better agreement with dispersive treatments. Finally, we briefly discuss magnetic moments and show how our techniques can help ...


Kinetic Theory Of Random Graphs: From Paths To Cycles, E. Ben-Naim, P.L. Krapivsky Dec 2005

Kinetic Theory Of Random Graphs: From Paths To Cycles, E. Ben-Naim, P.L. Krapivsky

Eli Ben-Naim

Structural properties of evolving random graphs are investigated. Treating linking as a dynamic aggregation process, rate equations for the distribution of node to node distances (paths) and of cycles are formulated and solved analytically. At the gelation point, the typical length of paths and cycles, l, scales with the component size k as l ~ k^{1/2}. Dynamic and finite-size scaling laws for the behavior at and near the gelation point are obtained. Finite-size scaling laws are verified using numerical simulations.


Ac Loss And Thickness Dependence Of Critical Currents In Coated Conductors, Anota Oluwatoyin Ijaduola Dec 2005

Ac Loss And Thickness Dependence Of Critical Currents In Coated Conductors, Anota Oluwatoyin Ijaduola

Doctoral Dissertations

This program of research is directed toward understanding the physical properties of certain materials in superconductive “coated conductors.” Specifically investigated were Ni1−xWx alloys for use as substrate and thin films of YBa 2Cu3O7, a high- Tc superconductor with many attractive features. A study has been conducted on the magnetic properties of a series of biaxially textured Ni1−xWx materials with compositions x = 0, 3, 5, 6, and 9 at.% W. These materials are important as substrates for “RABiTS”-type coated conductors that incorporate high temperature superconductors for current transport. The quasi-static dc and ac ...


Physics Department News, December 2005, College Of Arts And Sciences Dec 2005

Physics Department News, December 2005, College Of Arts And Sciences

Physics Newsletter

Contents from Volume 4, Issue 1:

  • A Note from the Editor
  • From the Chair
  • What’s New at the University
  • Faculty Highlights
  • Staff Highlights
  • ICPEAC 2009
  • Year of Physics 2005
  • PhysTEC
  • Alumni News
  • Student News
  • Annual Student Awards
  • Recent Graduates
  • Department Roster
  • Feedback/Update Reply For


Study Of The N = 77 Isotones Near The Proton-Drip Line; Isomeric Decays Of 140Eu, 142Tb, 144Ho, And 146Tm, Mohammed Noor Tantawy Dec 2005

Study Of The N = 77 Isotones Near The Proton-Drip Line; Isomeric Decays Of 140Eu, 142Tb, 144Ho, And 146Tm, Mohammed Noor Tantawy

Doctoral Dissertations

In this dissertation, the systematics of the [pi]h₁₁/₂ [tensor] [nu]h₁₁/₂ and [pi]h₁₁/₂ [tensor] [nu]s₁/₂ isomeric configurations were studied for the odd-Z, N = 77 isotones near the proton drip line. The isomeric decays in ¹⁴⁰Eu, ¹⁴²Tb, ¹⁴⁴Ho and ¹⁴⁶Tm were measured by means of X-ray, [gamma]-ray and charged particle spectroscopy at the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). The spin and parity of I[pi] = 8⁺ and 5⁻ were deduced for the isomers in ¹⁴⁰ Eu and ¹⁴²Tb. New decay schemes ...


Photo-Acoustic Analysis Of Dental Materials And Tissue, Pavlina Jetchkova Jeleva Dec 2005

Photo-Acoustic Analysis Of Dental Materials And Tissue, Pavlina Jetchkova Jeleva

Doctoral Dissertations

The goal of the presented study is the investigation of the feasibility of using optically generated acoustic waves for analysis of dental material below laser-ablation threshold.

The temperature rise of dental material and tissue has been modeled analytically and numerically, and measured experimentally. Following interactions with nano- and femto-second laser radiation the temperature rises at a rate of typically 1 ±C per J=cm2, along with the generation of an acoustical wave. The results from the models agree with the experiment. The acoustic measurements show differences in the acoustic signal strength and the frequency spectrum when the canal in ...


Gravity In Extra Dimensions Of Infinite Volume, Chad Aaron Middleton Dec 2005

Gravity In Extra Dimensions Of Infinite Volume, Chad Aaron Middleton

Doctoral Dissertations

In this thesis, we discuss various aspects of the Dvali-Gabadadze-Porrati (DGP) model in D-dimensions. Firstly, we generalize the DGP model, which consists of a delta-function type 3-brane embedded in an infinite volume bulk-space by allowing the 3-brane to have a finite thickness. We calculate the graviton propagator in the harmonic gauge both inside and outside the brane and discuss its dependence on the thickness of the brane. We obtain two infinite towers of massive modes and tachyonic ghosts. In the thin-brane limit, we recover the four-dimensional Einstein gravity behavior of the graviton propagator which was found in the delta-function treatment ...


Focused-Laser Interferometric Position Sensor, Stephen J. Friedman, Brett E. Barwick, Herman Batelaan Dec 2005

Focused-Laser Interferometric Position Sensor, Stephen J. Friedman, Brett E. Barwick, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

We describe a simple method to measure the position shifts of an object with a range of tens of micrometers using a focused-laser (FL) interferometric position sensor. In this article we examine the effects of mechanical vibration on FL and Michelson interferometers. We tested both interferometers using vibration amplitudes ranging from 0 to 20 μm. Our FL interferometer has a resolution much better than the diffraction grating periodicities of 10 and 14 μm used in our experiments. A FL interferometer provides improved mechanical stability at the expense of spatial resolution. Our experimental results show that Michelson interferometers cannot be used ...


Klein Paradox With Spin-Resolved Electrons And Positrons, P Krekora, Q Su, Rainer Grobe Dec 2005

Klein Paradox With Spin-Resolved Electrons And Positrons, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

Using numerical solutions to relativistic quantum field theory with space-time resolution, we illustrate how an incoming electron wave packet with a definite spin scatters off a supercritical potential step. We show that the production rate is reduced of only those electrons that have the same spin as the incoming electron is reduced. This spin-resolved result further clarifies the importance of the Pauli-exclusion principle for the Klein paradox.


The Ds/Cft Correspondence And Quasinormal Modes Of Black Holes, Scott Henry Ness Dec 2005

The Ds/Cft Correspondence And Quasinormal Modes Of Black Holes, Scott Henry Ness

Doctoral Dissertations

In this thesis we discuss two aspects of quantum gravity and break it up in the following way. In part I, we discuss a scalar field theory living in de Sitter space-time. We may describe the infinite past or future as being boundaries of this space-time and, on these boundaries we construct a field theory. It has been shown by Strominger that there exists a correspondence between the bulk de Sitter space-time and the field theory living in the infinite past [1]. This may be described as a holographic principle, where information in the bulk de Sitter space-time corresponds to ...


Climatology Of F Region Zonalplasma Drifts Over Jicamarca, Bela G. Fejer, J. R. Souza, A. S. Santos, A. E. Costa Pereira Dec 2005

Climatology Of F Region Zonalplasma Drifts Over Jicamarca, Bela G. Fejer, J. R. Souza, A. S. Santos, A. E. Costa Pereira

Bela G. Fejer

[1] We use extensive incoherent scatter radar observations made at the Jicamarca Radio Observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the F region peak using Bernstein polynomials as base functions. Our quiet-time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent. The nighttime drifts are eastward, have larger magnitudes, and increase strongly with solar flux, particularly near equinox and December solstice. Enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night. The nighttime drift ...


Nonrelativistic Qed Approach To The Lamb Shift, Ulrich D. Jentschura, Andrzej Czarnecki, Krzysztof Pachucki Dec 2005

Nonrelativistic Qed Approach To The Lamb Shift, Ulrich D. Jentschura, Andrzej Czarnecki, Krzysztof Pachucki

Physics Faculty Research & Creative Works

We calculate the one- and two-loop corrections of order α(Zα)6 and α2(Zα)6, respectively, to the Lamb shift in hydrogenlike systems using the formalism of nonrelativistic quantum electrodynamics. We obtain general results valid for all hydrogenic states with nonvanishing orbital angular momentum and for the normalized difference of S states. These results involve the expectation value of local effective operators and relativistic corrections to Bethe logarithms. The one-loop correction is in agreement with previous calculations for the particular cases of S, P, and D states. The two-loop correction in the order α2(Zα)6 includes ...


Mutual Ionization In 200-Kev H⁻+ He Collisions, T. Ferger, Daniel Fischer, Michael Schulz, R. Moshammer, A. B. Voitkiv, B. Najjari, J. Ullrich Dec 2005

Mutual Ionization In 200-Kev H⁻+ He Collisions, T. Ferger, Daniel Fischer, Michael Schulz, R. Moshammer, A. B. Voitkiv, B. Najjari, J. Ullrich

Physics Faculty Research & Creative Works

We studied mutual ionization in 200-keV H-+He collisions in a kinematically complete experiment by measuring the fully momentum-analyzed recoil ions and both active electrons in coincidence. Comparison of the data to our calculations, based on various theoretical models, show that mutual ionization proceeds predominantly through the interaction between both electrons. The post-collision interaction between the outgoing ejected electrons as well as higher order processes involving the interaction between the core of both collision partners are also important.


Photonic Bandgaps Of Conformally Coated Structures, Rana Biswas, Jinho Ahn, Taoho Lee, Jae-Hwang Lee, Yong-Sung Kim, Chang-Hwan Kim, Wai Y. Leung, Cha-Hwan Oh, Kristen P. Constant, Kai-Ming Ho Dec 2005

Photonic Bandgaps Of Conformally Coated Structures, Rana Biswas, Jinho Ahn, Taoho Lee, Jae-Hwang Lee, Yong-Sung Kim, Chang-Hwan Kim, Wai Y. Leung, Cha-Hwan Oh, Kristen P. Constant, Kai-Ming Ho

Materials Science and Engineering Publications

Polymeric molds of the layer-by-layer photonic crystal can be economically synthesized with a microtransfer molding technique. The refractive indices of these molds are low, preventing formation of a photonic bandgap. We find that such molds can be conformally coated with higher-index material. Photonic band calculations find structures in which conformally coated layer-by-layer molds have complete bandgaps for both titania and silicon coatings. Large stop bands exist in the 001 stacking direction. Feasibility of experimental conformal coating of the molds has been demonstrated with a titania-coated polyurethane mold, which shows optical features in agreement with simulations of reflection and transmission.