Physics Commons^™

3d Plasmonic Design Approach For Efficient Transmissive Huygens Metasurfaces, Bryan M. Adomanis, D. Bruce Burckel, Michael A. Marciniak

Faculty Publications

In this paper we present a design concept for 3D plasmonic scatterers as high- efficiency transmissive metasurface (MS) building blocks. A genetic algorithm (GA) routine partitions the faces of the walls inside an open cavity into a M x N grid of voxels which can be either covered with metal or left bare, and optimizes the distribution of metal coverage needed to generate electric and magnetic modes of equal strength with a targeted phase delay (Φt) at the design wavelength. Even though the electric and magnetic modes can be more complicated than typical low order modes, with their spectral overlap …

Photonic Topological Chern Insulators Based On Tellegen Metacrystals, Daniel A. Jacobs, Andrey E. Miroshnichenko, Yuri S. Kivshar, Alexander B. Khanikaev

Publications and Research

We demonstrate that topologically nontrivial states of light can be engineered in periodic photonic structures containing media with a Tellegen-type bianisotropic response. Whilst in such bianisotropic materials the time-reversal symmetry is broken, they are characterized by an intrinsic magnetic order which does not require macroscopic magnetization. Our design can therefore be considered as a direct analog of the solid state Chern insulator which exhibits a topological order in the absence of an external bias. Numerical simulations of such Tellegen photonic crystals reveal the existence of one way edge transport at domain walls and perfectly conducting boundaries not sensitive to structural …

Temperature Dependence Of Anisotropic Magnetoresistance In Antiferromagnetic Sr2Iro4, C. Wang, H. Seinige, Gang Cao, J.-S. Zhou, J. B. Goodenough, M. Tsoi

Center for Advanced Materials Faculty Publications

Temperature-dependent magnetotransport properties of the antiferromagnetic semiconductor Sr₂IrO₄ are investigated with point-contact devices. The point-contact technique allows to probe very small volumes and, therefore, to look for electronic transport on a microscopic scale. Point-contact measurements with single crystals of Sr₂IrO₄ were intended to see whether the additional local resistance associated with a small contact area between a sharpened Cu tip and the antiferromagnet shows magnetoresistance (MR) such as that seen in bulk crystals. Point-contact measurements at liquid nitrogen temperature revealed large MRs (up to 28%) for modest magnetic fields (250 mT) applied within an …

Modelling Two-Dimensional Photopolymer Patterns Produced With Multiple-Beam Holography, Dana Mackey, Tsvetanka Babeva, Izabela Naydenova, Vincent Toal

Conference papers

Periodic structures referred to as photonic crystals attract considerable interest due to their potential applications in areas such as nanotechnology, photonics, plasmonics, etc. Among various techniques used for their fabrication, multiple-beam holography is a promising method enabling defect-free structures to be produced in a single step over large areas.

In this paper we use a mathematical model describing photopolymerisation to simulate two-dimensional structures produced by the interference pattern of three noncoplanar beams. The holographic recording of different lattices is studied by variation of certain parameters such as beam wave vectors, time and intensity of illumination.

Coupled Photonic Crystal Micro-Cavities With Ultra-Low Threshold Power For Stiumulated Raman Scattering, Qiang Liu, Zhengbiao Ouyang, Sacharia Albin

Electrical & Computer Engineering Faculty Publications

We propose coupled cavities to realize a strong enhancement of the Raman scattering. Five sub cavities are embedded in the photonic crystals. Simulations through finite-difference time-domain (FDTD) method demonstrate that one cavity, which is used to propagate the pump beam at the optical-communication wavelength, has a Q factor as high as 1.254 × 10⁸ and modal volume as small as 0.03μm³ (0.3192(λ/n)³). These parameters result in ultra-small threshold lasing power ~17.7nW and 2.58nW for Stokes and anti-Stokes respectively. The cavities are designed to support the required Stokes and anti-Stokes modal spacing in silicon. The proposed structure …

Ultraviolet Lasing In High-Order Bands Of Three-Dimensional Zno Photonic Crystals, Michael Scharrer, Alexey Yamilov, Xiaohua Wu, Hui Cao, Robert P. H. Chang

Physics Faculty Research & Creative Works

UV lasing in three-dimensional ZnO photonic crystals is demonstrated at room temperature. The photonic crystals are inverse opals with high refractive index contrast that simultaneously confine light and provide optical gain. Highly directional lasing with tunable wavelength is obtained by optical pumping. Comparison of the experimental results to the calculated band structure shows that lasing occurs in high-order bands with abnormally low group velocity. This demonstrates that the high-order band structure of three-dimensional photonic crystals can be used to effectively confine light and enhance emission. Our findings may also impact other applications of photonic crystal devices. ©2006 American Institute of …

Photonic Band Structure Of Zno Photonic Crystal Slab Laser, Alexey Yamilov, X. Wu, Hui Cao

Physics Faculty Research & Creative Works

We recently reported on the realization of ultraviolet photonic crystal laser based on zinc oxide [Appl. Phys. Lett. 85, 3657 (2004)]. Here we present the details of structural design and its optimization. We develop a computational supercell technique that allows a straightforward calculation of the photonic band structure of ZnO photonic crystal slab on sapphire substrate. We find that despite the small index contrast between the substrate and the photonic layer, the low-order eigenmodes have predominantly transverse-electric (TE) or transverse-magnetic polarization. Because emission from ZnO thin film shows a strong TE preference, we are able to limit our consideration to …

Fabrication Of Inverted Opal Zno Photonic Crystals By Atomic Layer Deposition, Michael Scharrer, Xiaohua Wu, Alexey Yamilov, Hui Cao, Robert P. H. Chang

Physics Faculty Research & Creative Works

We have fabricated three-dimensional optically active ZnO photonic crystals by infiltrating polystyrene opal templates using a low-temperature atomic layer deposition process. The polystyrene is removed by firing the samples at elevated temperatures, and reactive ion etching is used to remove the top layer of ZnO and expose the (111) photonic crystal surface. The resulting structures have high filling fractions, possess photonic band gaps in the near-UV to visible spectrum, and exhibit efficient photoluminescence.

Ultraviolet Photonic Crystal Laser, Alexey Yamilov, Hui Cao, Robert P. H. Chang, Xiaohua Wu, Xang Liu, Shuyou Li, Vinayak P. Dravid

Physics Faculty Research & Creative Works

We fabricated two-dimensional photonic crystal structures in zinc oxide films with focused-ion-beam etching. Lasing is realized in the near-ultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in the strongly localized defect modes near the edges of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process. ©2004 American Institute of Physics

Loss And Dispersion Analysis Of Microstructured Fibers By Finite-Difference Method, Shangping Guo, Feng Wu, Sacharia Albin, Hsiang Tai, Robert S. Rogowski

Electrical & Computer Engineering Faculty Publications

The dispersion and loss in microstructured fibers are studied using a full-vectorial compact-2D finite-difference method in frequency-domain. This method solves a standard eigen-value problem from the Maxwell’s equations directly and obtains complex propagation constants of the modes using anisotropic perfectly matched layers. A dielectric constant averaging technique using Ampere’s law across the curved media interface is presented. Both the real and the imaginary parts of the complex propagation constant can be obtained with a high accuracy and fast convergence. Material loss, dispersion and spurious modes are also discussed.

Photonic Band Gap Analysis Using Finite-Difference Frequency-Domain Method, Shangping Guo, Feng Wu, Sacharia Albin

Electrical & Computer Engineering Faculty Publications

A finite-difference frequency-domain (FDFD) method is applied for photonic band gap calculations. The Maxwell’s equations under generalized coordinates are solved for both orthogonal and non-orthogonal lattice geometries. Complete and accurate band gap information is obtained by using this FDFD approach. Numerical results for 2D TE/TM modes in square and triangular lattices are in excellent agreements with results from plane wave method (PWM). The accuracy, convergence and computation time of this method are also discussed.

Simple Plane Wave Implementation For Photonic Crystal Calculations, Shangping Guo, Sacharia Albin

Electrical & Computer Engineering Faculty Publications

A simple implementation of plane wave method is presented for modeling photonic crystals with arbitrary shaped ‘atoms’. The Fourier transform for a single ‘atom’ is first calculated either by analytical Fourier transform or numerical FFT, then the shift property is used to obtain the Fourier transform for any arbitrary supercell consisting of a finite number of ‘atoms’. To ensure accurate results, generally, two iterating processes including the plane wave iteration and grid resolution iteration must converge. Analysis shows that using analytical Fourier transform when available can improve accuracy and avoid the grid resolution iteration. It converges to the accurate results …