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Full-Text Articles in Engineering
Temporally Multiplexed Ladar Polarimeter, Christian Keyser, Richard Kenneth Martin
Temporally Multiplexed Ladar Polarimeter, Christian Keyser, Richard Kenneth Martin
AFIT Patents
In a polarimeter, a polarization modulator changes a polarization phase of an output optical pulse with a modulation function that varies in time over the duration of the optical pulse. A static polarization state analyzer, which includes a one or more static polarization component analyzers and detectors, receives the modulated optical pulse after interaction with a target medium and provides time varying intensities of the polarization components of the received pulse. A signal processing module determines a polarization property of the target medium, such as a Mueller matrix, dependent upon time varied intensities over the duration of the received optical …
A Computationally-Efficient Bound For The Variance Of Measuring The Orientation Of Single Molecules, Tingting Wu, Tianben Ding, Hesam Mazidi, Oumeng Zhang, Matthew D. Lew
A Computationally-Efficient Bound For The Variance Of Measuring The Orientation Of Single Molecules, Tingting Wu, Tianben Ding, Hesam Mazidi, Oumeng Zhang, Matthew D. Lew
Electrical & Systems Engineering Publications and Presentations
Modulating the polarization of excitation light, resolving the polarization of emitted fluorescence, and point spread function (PSF) engineering have been widely leveraged for measuring the orientation of single molecules. Typically, the performance of these techniques is optimized and quantified using the Cramér-Rao bound (CRB), which describes the best possible measurement variance of an unbiased estimator. However, CRB is a local measure and requires exhaustive sampling across the measurement space to fully characterize measurement precision. We develop a global variance upper bound (VUB) for fast quantification and comparison of orientation measurement techniques. Our VUB tightly bounds the diagonal elements of the …
Electrostatic Design And Conditioning Of A Triple Point Junction Shield For A −200 Kv Dc High Voltage Photogun, G. Palacios-Serrano, F. Hannon, C. Hernandez-Garcia, M. Poelker, H. Baumgart
Electrostatic Design And Conditioning Of A Triple Point Junction Shield For A −200 Kv Dc High Voltage Photogun, G. Palacios-Serrano, F. Hannon, C. Hernandez-Garcia, M. Poelker, H. Baumgart
Electrical & Computer Engineering Faculty Publications
Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal −130 kV to −200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum …
Stress-Induced Birefringence And Fabrication Of In-Fiber Polarization Devices By Controlled Femtosecond Laser Irradiations, Lei Yuan, Baokai Cheng, Jie Huang, Jie Liu, Hanzheng Wang, Xinwei Lan, Hai Xiao
Stress-Induced Birefringence And Fabrication Of In-Fiber Polarization Devices By Controlled Femtosecond Laser Irradiations, Lei Yuan, Baokai Cheng, Jie Huang, Jie Liu, Hanzheng Wang, Xinwei Lan, Hai Xiao
Electrical and Computer Engineering Faculty Research & Creative Works
Optical birefringence was created in a single-mode fiber by introducing a series of symmetric cuboid stress rods on both sides of the fiber core along the fiber axis using a femtosecond laser. The stress-induced birefringence was estimated to be 2.4 x 10-4 at the wavelength of 1550 nm. By adding the desired numbers of stressed rods, an in-fiber quarter waveplate was fabricated with a insertion loss of 0.19 dB. The stressinduced birefringence was further explored to fabricate in-fiber polarizers based on the polarization-dependent long-period fiber grating (LPFG) structure. A polarization extinction ratio of more than 20 dB was observed …
Flexoelectric Polarization Studies In Bent-Core Nematic Liquid Crystals, S. Sreenilayam, Yuri Panarin, J. K. Vij, S. I. Torgova, A. Lehmann, C. Tschierske
Flexoelectric Polarization Studies In Bent-Core Nematic Liquid Crystals, S. Sreenilayam, Yuri Panarin, J. K. Vij, S. I. Torgova, A. Lehmann, C. Tschierske
Articles
The flexoelectric polarization (Pf) of four bent-core nematic liquid crystals (LCs) has been measured using the pyroelectric effect. Hybrid aligned nematic cells are fabricated for measuring the pyroelectric response over the entire range of the nematic phase. It is found that the magnitude of flexoelectric polarization Pf and the sum of the flexoelectric coefficients |e1 +e3| for the bent-core LCs studied here are three to six times higher than for the calamitics. Pf is found to depend on the transverse dipole moment of LC molecules. However,|e1 +e3| values are by no means giant as |e3| alone had been reported for …
Electromagnetic Cell With Three-Dimensional Polarization Dynamic Control, Bo O. Zhu, Weng Cho Chew, Lijun Jiang
Electromagnetic Cell With Three-Dimensional Polarization Dynamic Control, Bo O. Zhu, Weng Cho Chew, Lijun Jiang
Electrical and Computer Engineering Faculty Research & Creative Works
An electromagnetic (EM) cell is demonstrated to create the uniform electric field with 3-D polarization dynamic control for the EM compatibility/ interference (EMC/EMI) testing. We utilize 3-D orthogonal slotline structures to build the walls of the EM cell and produce uniform electric field inside the cell by feeding the slotlines in phase and terminating them with matching loads. The uniform electric field is similar to a standing wave produced by the slotline modes propagating in opposite directions. Microwave switches are integrated into the slotlines so that we can choose the operating slotline dynamically and change its orientation in a 3-D …
Properties Of Non-Tilted Bent-Core Orthogonal Smectic Liquid Crystal, S. Sreenilayam, M. Nagaraj, Yuri Panarin, J. K. Vij, A. Lehmann, C. Tschierske
Properties Of Non-Tilted Bent-Core Orthogonal Smectic Liquid Crystal, S. Sreenilayam, M. Nagaraj, Yuri Panarin, J. K. Vij, A. Lehmann, C. Tschierske
Articles
We present the properties of different achiral orthogonal polar smectic phases observed in a homologous series of bent-core molecular compounds. The macroscopically uniaxial SmAPR phase transforms to biaxial state by the application of higher electric fields and biaxial SmAPA phase undergoes biaxial-uniaxial-biaxial texture transformation with increasing electric fields,i.e.,initial antiferroelectric structure transforms into ferroelectric state under higher electric fields and it shows three different optically distinguishable states. The SmAPAR phase shows an entirely different response compared to other polar smectic phases under study. The dielectric measurements in the SmAPAR phase is the evidence of antiferroelectric behavior of uniaxial state. The polarizing …
Optical Encryption As A Function Of Polarization In Optical Fiber Communications, Syed H. Murshid, Hari Priya Muralikrishnan, Jayachandran Tamilarasan, Abhijit Chakravarty, John H. Caulfield
Optical Encryption As A Function Of Polarization In Optical Fiber Communications, Syed H. Murshid, Hari Priya Muralikrishnan, Jayachandran Tamilarasan, Abhijit Chakravarty, John H. Caulfield
Electrical Engineering and Computer Science Faculty Publications
An optical encryption technique based on polarization property of light is proposed. Many techniques using polarization beam splitters to encrypt the signal have been proposed earlier. They are based on splitting and interference of two light signals, namely message and noise. Only by placing suitable mirrors and a second beam splitter in a suitable position, the two signals are reconstructed at the output. In this paper we report the fiber optic version of a polarization based encryption technique that also has the potential to double the data carrying capacity of the fiber. Using polarization dependent couplers in the fiber optic …
Stokes Antenna Temperatures, David G. Long, Jeffrey R. Piepmeier, Eni G. Njoku
Stokes Antenna Temperatures, David G. Long, Jeffrey R. Piepmeier, Eni G. Njoku
Faculty Publications
The growing importance of polarimetric radiometers has led to the need for a detailed theory for Stokes antenna temperatures. In this paper, we provide a full Stokes vector formulation of an antenna temperature that accounts for the entire antenna pattern, which includes polarization mixing in the main-beam and sidelobe effects. To derive the Stokes antenna temperatures, we follow the conventional methods in the Earth remote sensing literature while relying on a coherency algebra approach from radio astronomy. Connections and parallels to the conventional approaches are noted along the way. We also introduce generalizations of beam efficiency and cross polarization for …
Polarization Rotation Correction In Radiometry: An Error Analysis, David G. Long, Derek Hudson, Jeffrey R. Piepmeier
Polarization Rotation Correction In Radiometry: An Error Analysis, David G. Long, Derek Hudson, Jeffrey R. Piepmeier
Faculty Publications
Yueh proposed a method of using the third Stokes parameter TU to correct brightness temperatures such as Tv and Th for polarization rotation. This paper presents an extended error analysis of the estimation of Tv , Th, and TQ equiv Tv - Th by Yueh's method. In order to carry out the analysis, we first develop a forward model of polarization rotation that accounts for the random nature of thermal radiation, receiver noise, and (to first order) calibration. Analytic formulas are then derived for the bias, standard deviation (STD), and root-mean-square error (RMSE) of estimated TQ, Tv , and Th, …
Polarization Dependence Of Bend Loss For A Standard Singlemode Fiber, Qian Wang, Ginu Rajan, Pengfei Wang, Gerald Farrell
Polarization Dependence Of Bend Loss For A Standard Singlemode Fiber, Qian Wang, Ginu Rajan, Pengfei Wang, Gerald Farrell
Articles
Polarization dependence of bend loss caused by the polymer coating layer for a standard singlemode fiber (SMF28) is investigated theoretically and experimentally. Bend loss for SMF28 for both the TE and TM mode is calculated separately. Normalized polarization dependent loss is proposed for the characterization of the polarization sensitivity of bend loss for different bend radii. Corresponding experimental tests are presented, which agree with the theoretical results. Both the theoretical and experimental results show that the polymer coating layer has a significant influence on the polarization dependence of bend loss.
Automatic Detection And Validity Of The Sea-Ice Edge: An Application Of Enhanced-Resolution Quikscat/Seawinds Data, David G. Long, Jorg Haarpaintner, Rasmus T. Tonboe, Michael L. Van Woert
Automatic Detection And Validity Of The Sea-Ice Edge: An Application Of Enhanced-Resolution Quikscat/Seawinds Data, David G. Long, Jorg Haarpaintner, Rasmus T. Tonboe, Michael L. Van Woert
Faculty Publications
Sea-ice edge detection is an essential task at the different national ice services to secure navigation in ice-covered seas. Comparison between the Remund and Long ice mask image from enhanced-resolution QuikScat/SeaWinds (QS) products and the analyzed ice edge from high-resolution RADARSAT synthetic aperture radar has shown that the automatically determined QS ice mask underestimates the Arctic ice extent. QS data was statistically analyzed by colocating the data with ice charts around Greenland and with the National Aeronautics and Space Administration Team's Special Sensor Microwave/Imager (SSM/I) ice concentration algorithm over the whole Arctic region. All variables, i.e., the backscatter in vertical …
Influence Of Antenna Aiming On Ece In Mast, Josef Preinhaelter, Jakub Urban, Pavol Pavlo, Vladimir Shevchenko, Martin Valovič, Linda L. Vahala, George Vahala
Influence Of Antenna Aiming On Ece In Mast, Josef Preinhaelter, Jakub Urban, Pavol Pavlo, Vladimir Shevchenko, Martin Valovič, Linda L. Vahala, George Vahala
Electrical & Computer Engineering Faculty Publications
The effect of the direction of the detected beam on the intensity of ECE is studied. It is found that the combined effects of the strong dependence of the conversion efficiencey of O mode at the plasma resonance on the direction of the incident wave and the partial screening of the beam waist by the MAST vessel wall, can be responsible for the weakening of ECE emission for some frequencies. The theoretical model for ECE data interpretation on MAST has been significantly improved. New features of the model are as follows: the quasioptical treatment of the receiving antenna, interference, polarization …
Polarization Effects In Photoluminescence Of C- And M-Plane Gan/Algan Multiple Quantum Wells, E. Kuokstis, C. Q. Chen, M. E. Gaevski, W. H. Sun, J. W. Yang, Grigory Simin, M. Asif Khan, H. P. Maruska, D. W. Hill, M. C. Chou, J. J. Gallagher, B. Chai
Polarization Effects In Photoluminescence Of C- And M-Plane Gan/Algan Multiple Quantum Wells, E. Kuokstis, C. Q. Chen, M. E. Gaevski, W. H. Sun, J. W. Yang, Grigory Simin, M. Asif Khan, H. P. Maruska, D. W. Hill, M. C. Chou, J. J. Gallagher, B. Chai
Faculty Publications
Polarizationeffects have been studied in GaN/AlGaN multiple quantum wells(MQWs) with different c-axis orientation by means of excitation-dependent photoluminescence(PL) analysis. Quantum structures were grown on [0001]-oriented sapphire substrates (C plane) and single-crystalline [11̄00]-oriented freestanding GaN (M plane) using the metalorganic chemical vapor deposition technique. Strong PL spectrum line blueshifts (up to 140 meV) which are correlated with the excitation intensity have been obtained for C-plane MQWs, whereas no shift has been observed for M-plane MQWs.Theoretical calculations and comparison with the PL data confirm that the built-in electric field for C-plane structures is much stronger than the field present for M-plane MQWs. …
Differential Signalling In Pcbs: Modeling And Validation Of Dielectric Losses And Effects Of Discontinuities, R. Araneo, Chen Wang, Xiaoxiong Gu, S. Celozzi, James L. Drewniak
Differential Signalling In Pcbs: Modeling And Validation Of Dielectric Losses And Effects Of Discontinuities, R. Araneo, Chen Wang, Xiaoxiong Gu, S. Celozzi, James L. Drewniak
Electrical and Computer Engineering Faculty Research & Creative Works
This paper focuses on differential signal transmission above ground planes with gaps, taking into account the dielectric and conductive losses of the substrate. An equivalent lumped-circuit is proposed and its suitability is investigated by comparing the obtained numerical results with the measured data. Furthermore the differential to common mode conversion of the waves, while crossing the gap, is theoretically analyzed and experimentally verified.
Finite-Aperture Wire Grid Polarizers, Michael A. Jensen, Gregory P. Nordin
Finite-Aperture Wire Grid Polarizers, Michael A. Jensen, Gregory P. Nordin
Faculty Publications
The transmission characteristics of wire grid polarizers fabricated in finite apertures are investigated by using a three-dimensional finite-difference time-domain formulation. Specifically, the optical transmissivity and extinction ratio are characterized for a wide variety of geometrical parameters including aperture size in both dimensions, conducting wire fill factor, and polarizer thickness. A dispersive material model is used to investigate the performance of polarizers fabricated by using realistic metals at infrared wavelengths. The results indicate that the aperture dimension significantly impacts the polarizer transmission behavior and that the extinction of the unwanted polarization is often limited by depolarizing scattering that is due to …
Application Of A Hybrid Fem/Mom Method To A Canonical Pcb Problem, Yun Ji, J. Chen, Todd H. Hubing, James L. Drewniak
Application Of A Hybrid Fem/Mom Method To A Canonical Pcb Problem, Yun Ji, J. Chen, Todd H. Hubing, James L. Drewniak
Electrical and Computer Engineering Faculty Research & Creative Works
A hybrid FEM/MOM method was used to solve a canonical printed circuit board (PCB) problem. The PCB is populated with three traces. One is a signal line and the other two are I/O lines that extend beyond the boundary of the board. The finite element method (FEM) was used to model the fields in the volume around the on-board trace. The method of moments (MOM) was employed to model the equivalent surface currents on the board and the current on the off-board traces. The FEM and MOM equations were coupled by forcing the continuity of tangential fields on the dielectric …
The Synthesis Of Patterns Using A Series-Fed Array Of Annular Sector Radiating Line (Anserlin) Elements: Low-Profile, Circularly Polarized Radiators, James L. Drewniak, P. E. Mayes
The Synthesis Of Patterns Using A Series-Fed Array Of Annular Sector Radiating Line (Anserlin) Elements: Low-Profile, Circularly Polarized Radiators, James L. Drewniak, P. E. Mayes
Electrical and Computer Engineering Faculty Research & Creative Works
A series-fed, circularly polarized array of annular sector radiating-line elements that operates over a ground plane and has a low profile is presented. Pattern shaping can be achieved through control of the fraction of the incident power that is radiated by each element. This can be accomplished over a wide range by a simple adjustment in the geometry of each element. A synthesis technique is given, and experimental results are presented. The array is demonstrated to have a high return loss (good impedance match) and a low axial ratio
Anserlin. A Broad-Band, Low-Profile, Circularly Polarized Antenna, James L. Drewniak, P. E. Mayes
Anserlin. A Broad-Band, Low-Profile, Circularly Polarized Antenna, James L. Drewniak, P. E. Mayes
Electrical and Computer Engineering Faculty Research & Creative Works
A technique is presented for improving the performance of low-profile, circularly polarized (CP) radiating-line antennas. The essential elements of the technique pertain to establishing a single traveling wave on an annular sector of conducting strip that is positioned parallel and close to a large conducting surface. The antenna is named the annular sector, radiating-line (ANSERLIN) antenna. Using this technique, the impedance bandwidth becomes so large that it no longer has any bearing on the operating bandwidth. Instead, the pattern shape and axial ratio become the factors that limit the bandwidth. Both senses of circular polarization can be transmitted or received …
A Log-Spiral, Radiating-Line Antenna, James L. Drewniak, P. E. Mayes, D. Tanner, R. Waller
A Log-Spiral, Radiating-Line Antenna, James L. Drewniak, P. E. Mayes, D. Tanner, R. Waller
Electrical and Computer Engineering Faculty Research & Creative Works
No abstract provided.