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2005

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Articles 1 - 30 of 45

Full-Text Articles in Optics

Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal Oct 2005

Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal

Faculty Publications

No abstract provided.

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Partition-Based Interpolation For Color Filter Array Demosaicking And Super-Resolution Reconstruction, Min Shao, Kenneth E. Barner, Russell C. Hardie Oct 2005

Partition-Based Interpolation For Color Filter Array Demosaicking And Super-Resolution Reconstruction, Min Shao, Kenneth E. Barner, Russell C. Hardie

Electrical and Computer Engineering Faculty Publications

A class of partition-based interpolators that addresses a variety of image interpolation applications are proposed. The proposed interpolators first partition an image into a finite set of partitions that capture local image structures. Missing high resolution pixels are then obtained through linear operations on neighboring pixels that exploit the captured image structure. By exploiting the local image structure, the proposed algorithm produces excellent performance on both edge and uniform regions. The presented results demonstrate that partition-based interpolation yields results superior to traditional and advanced algorithms in the applications of color filter array (CFA) demosaicking and super-resolution reconstruction.

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Simulation Of Ultrashort Laser Pulse Propagation With High-Order Dispersion, Raman Scattering, And Shock Formation, Jeremy Gulley, Erik Zeek, William Dennis Sep 2005

Simulation Of Ultrashort Laser Pulse Propagation With High-Order Dispersion, Raman Scattering, And Shock Formation, Jeremy Gulley, Erik Zeek, William Dennis

Jeremy R. Gulley

No abstract is currently available.

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Harmonic Generation In Thin Films And Multilayers, William S. Kolthammer '04, Dustin Barnard '03, Nicole Carson, Aaron D. Edens '00, Nathan A. Miller '01, Peter N. Saeta Jul 2005

Harmonic Generation In Thin Films And Multilayers, William S. Kolthammer '04, Dustin Barnard '03, Nicole Carson, Aaron D. Edens '00, Nathan A. Miller '01, Peter N. Saeta

All HMC Faculty Publications and Research

A general method for computing harmonic generation in reflection and transmission from planar nonmagnetic multilayer structures is described. The method assumes plane waves and treats harmonic generation in the parametric approximation. The method is applied in studying the second- and third-harmonic generation properties of thin crystal silicon layers surrounded by thermal oxide. Most independent components of the nonlinear susceptibility tensor have unique signatures with silicon layer thickness d, allowing their strength to be determined in principle by measuring harmonic generation as a function of d. Surface and bulk contributions to third-harmonic generation are cleanly distinguished, with the bulk signal dominating. …

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Compression Of Laser Radiation In Plasmas Using Electromagnetic Cascading, Serguei Y. Kalmykov, Gennady Shvets Jun 2005

Compression Of Laser Radiation In Plasmas Using Electromagnetic Cascading, Serguei Y. Kalmykov, Gennady Shvets

Serge Youri Kalmykov

Compressing high-power laser beams in plasmas via generation of a coherent cascade of electromagnetic sidebands is described. The technique requires two copropagating beams detuned by a near-resonant frequency, \Omega < \omega_{p}. The ponderomotive force of the laser beat wave drives an electron plasma wave which modifies the refractive index of plasma so as to produce a periodic phase modulation of the laser field with the beat period t_b = 2\pi/\Omega. A train of chirped laser beat notes (each of duration t_b) is thus created. The group velocity dispersion of radiation in plasma can then compress each beat note to a few-laser-cycle duration. As a result, a train of sharp electromagnetic spikes separated in time by t_b is formed. Depending on the plasma and laser parameters, chirping and compression can be implemented either concurrently in the same plasma or sequentially in different plasmas.

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Pixel Entanglement: Experimental Realization Of Optically Entangled D=3 And D=6 Qudits, Malcolm N. O'Sullivan, Irfan Ali Khan, Robert W. Boyd, John C. Howell Jun 2005

Pixel Entanglement: Experimental Realization Of Optically Entangled D=3 And D=6 Qudits, Malcolm N. O'Sullivan, Irfan Ali Khan, Robert W. Boyd, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

We demonstrate a simple experimental method for creating entangled qudits. Using transverse-momentum and position entanglement of photons emitted in spontaneous parametric down-conversion, we show entanglement between discrete regions of space, i.e., pixels. We map each photon onto as many as six pixels, where each pixel represents one level of our qudit state. The method is easily generalizable to create even higher dimensional, entangled states. Thus, the realization of quantum information processing in arbitrarily high dimensions is possible, allowing for greatly increased information capacity.

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Scene-Based Nonuniformity Correction Technique For Focal-Plane Arrays Using Readout Architecture, Balaji Narayanan, Russell C. Hardie, Robert A. Muse Jun 2005

Scene-Based Nonuniformity Correction Technique For Focal-Plane Arrays Using Readout Architecture, Balaji Narayanan, Russell C. Hardie, Robert A. Muse

Electrical and Computer Engineering Faculty Publications

Spatial fixed pattern noise is a common and major problem in modern infrared imagers due to the nonuniform response of the photodiodes in the focal plane array of the imaging system. In addition, the nonuniform response of the readout and the digitization electronics, involved in multiplexing the signals from the photodiodes, causes further nonuniformity. In this paper, we describe a novel scene based nonuniformity correction algorithm that treats the aggregate nonuniformity in separate stages. Firstly, the nonuniformity from the readout amplifiers is corrected using knowledge of the readout architecture of the imaging system. In the second stage, the nonuniformity resulting …

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X-Ray Generation From Metal Targets Coated With Wavelength-Scale Spheres, D. R. Symes, H. A. Sumeruk, I. V. Churina, Thomas D. Donnelly, J. Landry, T. Ditmire May 2005

X-Ray Generation From Metal Targets Coated With Wavelength-Scale Spheres, D. R. Symes, H. A. Sumeruk, I. V. Churina, Thomas D. Donnelly, J. Landry, T. Ditmire

All HMC Faculty Publications and Research

X-ray yield measurements from targets coated with wavelength-scale spheres are compared with measurements from polished targets. Evidence for a hotter resonant electron temperature due to field enhancements from Mie resonances in the spheres is investigated.

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Strongly Coupled Large-Angle Stimulated Raman Scattering Of Short Laser Pulse In Plasma-Filled Capillary, Serguei Y. Kalmykov, Patrick Mora Apr 2005

Strongly Coupled Large-Angle Stimulated Raman Scattering Of Short Laser Pulse In Plasma-Filled Capillary, Serguei Y. Kalmykov, Patrick Mora

Serge Youri Kalmykov

Strongly coupled large-angle stimulated Raman scattering sLA SRSd of a short intense laser pulse develops in a plane plasma-filled capillary differently than in a plasma with open boundaries. Coupling the laser pulse to a capillary seeds the LA SRS in the forward direction (scattering angle smaller than \pi / 2 ) and can thus produce a high instability level in the vicinity of the entrance plane. In addition, oblique mirror reflections off capillary walls partly suppress the lateral convection of scattered radiation and increase the growth rate of the SRS under arbitrary (not too small) angle. Hence, the saturated convective …

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Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak Apr 2005

Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak

Department of Physics Publications

Inspired by experimental observations of spatially ordered growth hillocks on the (001) surfaces of natural graphite crystals, a mechanism for spatial organization in quantum dotself-assembly is proposed. The regular arrangement of steps from a screw dislocation-generated growth spiral provides the overall template for such ordering. An ordered array of quantum dots may be formed or nucleated from impurities driven to the step corners by diffusion and by their interactions with the spiral’s steps and kinks. Kinetic Monte Carlo simulation of a solid-on-solid model supports the feasibility of such a mechanism.

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Deconvolution Analysis Of Laser Pulse Profiles From 3-D Ladar Temporal Returns, Michael D. Walter Mar 2005

Deconvolution Analysis Of Laser Pulse Profiles From 3-D Ladar Temporal Returns, Michael D. Walter

Theses and Dissertations

Three-dimensional laser imaging systems offer important advantages for battlefield applications, such as night-time targeting and tactical reconnaissance. Recently developed technologies used by coherent detection systems that collect temporally resolved images include arrays of Avalanche Photo-Diodes (APD), Geiger mode APDs, and photo-diodes. Frequently, LADAR systems produce waveforms from each detector that characterize the convolution of the transmitted laser pulse with the target surface. The pulse convolution generates uncertainty as to the precise location of a target surface, which can severely impact various weapon systems' targeting capability. This work analyzes two deconvolution techniques: Wiener filtering and an iterative process derived from the …

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Using Liquid Crystal Spatial Light Modulators For Closed Loop Tracking And Beam Steering With Phase Holography, Michael J. Perry Mar 2005

Using Liquid Crystal Spatial Light Modulators For Closed Loop Tracking And Beam Steering With Phase Holography, Michael J. Perry

Theses and Dissertations

Optical Phased Array (OPA) technology offers advantages in the reduction of size, weight, and power of optical steering devices. Nematic liquid crystal (LC) spatial light modulators (SLMs) have been studied as a potential candidate for building non-mechanical OPAs. They can steer a laser beam and split the beam into multiple beams. This thesis builds upon the prior research showing each split beam can be individually controlled, including variation in intensity. A closed loop tracking scenario shows the flexibility of the SLM by tracking and stabilizing an incoming beam. Results show that applying a phase grating to the SLM has limitations …

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Laser Wakefield Acceleration By Petawatt Ultrashort Laser Pulses, Leonid M. Gorbunov, Serguei Y. Kalmykov, Patrick Mora Feb 2005

Laser Wakefield Acceleration By Petawatt Ultrashort Laser Pulses, Leonid M. Gorbunov, Serguei Y. Kalmykov, Patrick Mora

Serge Youri Kalmykov

An ultrashort (about 30 fs) petawatt laser pulse focused with a wide focal spot (about 100 mm) in a rarefied plasma (n_0 ~ 10^{17} cm^{−3}) excites a nonlinear plasma wakefield which can accelerate injected electrons up to GeV energies without any pulse channeling. Under these conditions, propagation of the laser pulse with an overcritical power for relativistic self-focusing is almost the same as in vacuum. The nonlinear quasiplane plasma wave, whose amplitude and phase velocity vary along the laser path, effectively traps and accelerates injected electrons with a wide range of initial energies. Electrons accelerated over two Rayleigh lengths (about …

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Nonlinear Absorption, Scattering And Optical Limiting Studies Of Cds Nanoparticles, N. Venkatra, D. Narayana Rao, Murty Akundi Feb 2005

Nonlinear Absorption, Scattering And Optical Limiting Studies Of Cds Nanoparticles, N. Venkatra, D. Narayana Rao, Murty Akundi

Faculty and Staff Publications

The nonlinear optical absorption, scattering and optical limiting properties of CdS nanoparticles dispersed in dimethylformamide (DMF) are investigated. The nanoparticles are synthesized using the standard chemical synthesis method with thioglycerol as the capping agent. The investigations are carried out at 532 nm in the ns regime. Strong two-photon absorption and nonlinear scattering are found to be responsible for good optical limiting characteristics in these nanoparticles.

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Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock Jan 2005

Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock

Electronic Theses and Dissertations

The propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one- and two-dimensional waveguide lattices is presented. The ability to completely overcome the effects of discrete diffraction through the mutual trapping of two orthogonally polarized coherent beams interacting in Kerr nonlinear arrays of birefringent …

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Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan Jan 2005

Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan

Electronic Theses and Dissertations

This dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of the applications demonstrated in this thesis are LC devices that are non-pixelated and can be controlled either electrically or optically. Instead of the typical pixel-by-pixel control as is custom in LC devices, the phase profile across …

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Refractive Indices Of Liquid Crystals And Their Applications In Display And Photonic Devices, Jun Li Jan 2005

Refractive Indices Of Liquid Crystals And Their Applications In Display And Photonic Devices, Jun Li

Electronic Theses and Dissertations

Liquid crystals (LCs) are important materials for flat panel display and photonic devices. Most LC devices use electrical field-, magnetic field-, or temperature-induced refractive index change to modulate the incident light. Molecular constituents, wavelength, and temperature are the three primary factors determining the liquid crystal refractive indices: ne and no for the extraordinary and ordinary rays, respectively. In this dissertation, we derive several physical models for describing the wavelength and temperature effects on liquid crystal refractive indices, average refractive index, and birefringence. Based on these models, we develop some high temperature gradient refractive index LC mixtures for photonic applications, such …

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Simple Electronic Speckle Pattern Shearing Interferometer With A Holographic Grating As A Shearing Element, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal Jan 2005

Simple Electronic Speckle Pattern Shearing Interferometer With A Holographic Grating As A Shearing Element, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal

Conference Papers

An optical set-up for electronic speckle pattern shearing interferometry (ESPSI) using a photopolymer diffractive optical element as a shearing element, is presented. A laser beam illuminates the object at an angle to the normal to the object surface. The holographic diffraction grating is placed in front of the object. The zero and the first order of diffraction form the image and the sheared image of the object. The images are imaged onto the CCD camera, whose optical axis coincides with the normal to the object surface. The field of view is limited only by the dimensions of the photopolymer plate. …

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Characterisation Of An Acrylamide-Based Photopolymer For Data Storage Utilizing Holographic Angular Multiplexing, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, Vincent Toal Jan 2005

Characterisation Of An Acrylamide-Based Photopolymer For Data Storage Utilizing Holographic Angular Multiplexing, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, Vincent Toal

Articles

An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 18 to 30 gratings were angularly multiplexed in a volume of photopolymer layer at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength holographic gratings to be recorded. This investigation yielded the photopolymer M/# for moderately thin layers. Photopolymer temporal stability was also studied by measuring variations of material shrinkage, …

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A Compact Electronic Speckle Pattern Interferometry System Using A Photopolymer Reflection Holographic Optical Element, Guntaka Tulasi Sridhar Reddy, Raghavendra Jallapuram, Vincent Toal, Izabela Naydenova, Suzanne Martin, Svetlana Mintova Jan 2005

A Compact Electronic Speckle Pattern Interferometry System Using A Photopolymer Reflection Holographic Optical Element, Guntaka Tulasi Sridhar Reddy, Raghavendra Jallapuram, Vincent Toal, Izabela Naydenova, Suzanne Martin, Svetlana Mintova

Conference Papers

A simple and compact electronic speckle pattern interferometry system using a reflection holographic optical element is presented. The reflection holographic optical element is recorded on an acrylamide based photopolymer formulated and prepared at the Centre for Industrial & Engineering Optics. Light intensity of 40mW/cm2 with an exposure time of 60 seconds was used in fabricating the holographic optical element. The vibration mode patterns of a 4 cm diameter thin circular sheet of brass metal attached to a 4 cm diameter paper cone loud speaker are presented.

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Signal Flow Analysis, Partha P. Banerjee Jan 2005

Signal Flow Analysis, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

Signal flow graphs are a viable alternative to block diagrammatic representation of a system. What makes signal flow graphs attractive is that certain features from graph theory can be applied to the simplification and the synthesis of complex systems.

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Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging, Vesselin Chaoulov Jan 2005

Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging, Vesselin Chaoulov

Electronic Theses and Dissertations

A main challenge in the field of special effects is to create special effects in real time in a way that the user can preview the effect before taking the actual picture or movie sequence. There are many techniques currently used to create computer-simulated special effects, however current techniques in computer graphics do not provide the option for the creation of real-time texture synthesis. Thus, while computer graphics is a powerful tool in the field of special effects, it is neither portable nor does it provide work in real-time capabilities. Real-time special effects may, however, be created optically. Such approach …

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Interferometry-Based Free Space Communication And Information Processing, Muzamil Arshad Arain Jan 2005

Interferometry-Based Free Space Communication And Information Processing, Muzamil Arshad Arain

Electronic Theses and Dissertations

This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, …

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Spectral Signature Modification By Application Of Infrared Frequency-Selective Surfaces, Brian Monacelli Jan 2005

Spectral Signature Modification By Application Of Infrared Frequency-Selective Surfaces, Brian Monacelli

Electronic Theses and Dissertations

It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the …

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Electronic Speckle Pattern Shearing Interferometry For Nondestructive Testing Of Thermal Sprayed Alloy Coatings, Yueqiang Xue, David Kennedy, Emilia Mihaylova Jan 2005

Electronic Speckle Pattern Shearing Interferometry For Nondestructive Testing Of Thermal Sprayed Alloy Coatings, Yueqiang Xue, David Kennedy, Emilia Mihaylova

Conference Papers

Thermal sprayed coatings have wide engineering applications. There now exists a wide range of destructive and nondestructive testing (NDT) methods for surface coating inspections. This paper describes an application of Electronic Speckle Pattern Shearing Interferometry (ESPSI) for NDT of thermal sprayed surface coatings. In contrast to other conventional methods such as eddy current, ultrasonic or X-ray, ESPSI allows fast and large survey area inspection. Experimental results of shearographic measurements are presented. Thermal sprayed coatings were tested using ESPSI. Delaminations of the coatings were detected and the fringe patterns were captured using this method. It is shown that the shearography technique …

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Study Of An Acrylamide-Based Photopolymer For Use As A Holographic Data Storage Medium, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, G Berger, C Denz, Vincent Toal Jan 2005

Study Of An Acrylamide-Based Photopolymer For Use As A Holographic Data Storage Medium, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, G Berger, C Denz, Vincent Toal

Conference Papers

An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 15 to 30 gratings were angularly multiplexed in a volume of the photopolymer layers with different thickness at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength gratings to be recorded. From this investigation the photopolymer layer’s M/# was determined with regard to the recording geometry used. The temporal stability …

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Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal Jan 2005

Holographic Recording Of Patterns In Thin Film Acrylamide-Based Photopolymer, Izabela Naydenova, Kotakonda Pavani, Emilia Mihaylova, Katia Loudmer, Suzanne Martin, Vincent Toal

Conference Papers

A study of the light induced surface relief modulation in thin photopolymer layers is reported. Due to the nature of the photopolymer used no additional post-processing is required after holographic recording. An investigation of the dependence of the amplitude of the photoinduced relief modulation on different parameters of recording such as spatial frequency, intensity of the beams and times of exposure has been carried out. The surface relief modulation is characterized by white light interferometry. Photopolymer layer thickness ranges from 1-5m. A model of the mechanism of surface relief formation is proposed on the basis of the measured dependencies. A …

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Investigation Of Polymerization Rate In An Acrylamide-Based Photopolymer Using Raman Spectroscopy, Raghavendra Jallapuram, Izabela Naydenova, Hugh Byrne, Suzanne Martin, Robert Howard, Vincent Toal Jan 2005

Investigation Of Polymerization Rate In An Acrylamide-Based Photopolymer Using Raman Spectroscopy, Raghavendra Jallapuram, Izabela Naydenova, Hugh Byrne, Suzanne Martin, Robert Howard, Vincent Toal

Conference Papers

Diffusion models predict that polymerization and diffusion rates are the key factors that control the dynamics and the final properties of a holographic grating recorded in a photopolymerizable material. Diffusion rates during the initial phase of holographic recording have already been studied and reported. We now report the investigation of the polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy. The polymerization rate constant was estimated by monitoring the intensity of the characteristic Raman peaks at 1284 cm-1 corresponding to the bending mode of CH vinyl bond in acrylamide and 1609 cm-1 corresponding to the carbon-carbon double bond (C=C) in …

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Data Management And Visualization Of X-Ray Diffraction Spectra From Thin Film Ternary Composition Spreads, I. Takeuchi, C. J. Long, O. O. Famodu, M. Murakami, Jason R. Hattrick-Simpers, G. W. Rubloff, M. Stukowski, K. Rajan Jan 2005

Data Management And Visualization Of X-Ray Diffraction Spectra From Thin Film Ternary Composition Spreads, I. Takeuchi, C. J. Long, O. O. Famodu, M. Murakami, Jason R. Hattrick-Simpers, G. W. Rubloff, M. Stukowski, K. Rajan

Faculty Publications

We discuss techniques for managing and visualizing x-ray diffraction spectrum data for thin film composition spreads which map large fractions of ternary compositional phase diagrams. An in-house x-ray microdiffractometer is used to obtain spectra from over 500 different compositions on an individual spread. The MATLAB software is used to quickly organize the data and create various plots from which one can quickly grasp different information regarding structural and phase changes across the composition spreads. Such exercises are valuable in rapidly assessing the “overall” picture of the structural evolution across phase diagrams before focusing in on specific composition regions for detailed …

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Interphase Exchange Coupling In Fe/Sm-Co Bilayers With Gradient Fe Thickness, Ming-Hui Yu, Jason R. Hattrick-Simpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle Jan 2005

Interphase Exchange Coupling In Fe/Sm-Co Bilayers With Gradient Fe Thickness, Ming-Hui Yu, Jason R. Hattrick-Simpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle

Faculty Publications

We have fabricated Fe∕Sm–Co bilayers with gradient Fe thicknesses in order to systematically study the dependence of exchange coupling on the thickness of the Fe layer. The Fe layer was deposited at two different temperatures (150 and 300°C) to study the effect of deposition temperature on the exchange coupling. Magneto-optical Kerr effect and x-ray magnetic circular dichroism (XMCD) have been employed as nondestructive rapid characterization tools to map the magnetic properties of the gradient samples. Systematic enhancement in exchange coupling between the soft layer and the hard layer is observed as the soft layer thickness is decreased. Separate exchange couplings …

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