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214 results on '"Citrin D.S."'

1. Terahertz nondestructive stratigraphic reconstruction of paper stacks based on adaptive sparse deconvolution

Author

Zhai M., Locquet A., and Citrin D.S.

Subjects
terahertz time-domain spectroscopy, paper handling, super-resolution characterization, dispersion, sparse deconvolution, Applied optics. Photonics, TA1501-1820, Optics. Light, QC350-467
Abstract

Characterizing the number of sheets in a stack of paper typically involves mechanical separation of the individual sheets. Here, we explore an nondestructive method that can be applied to the intact paper stack. Namely, terahertz time-of-flight tomography, together with post signal-processing technique sparse deconvolution based on a two-step iterative shrinkage-thresholding algorithm (SD/TWIST), is employed to reconstruct the stratigraphy of stacks of sheets of paper with multilayered structure in a nondestructive and noncontact manner. The double-Gaussian mixture model (DGMM) is also incorporated to suppress dispersion in the reflected THz echoes. The effectiveness and accuracy of the proposed adaptive sparse-deconvolution method are verified experimentally and numerically. Compared with the commonly used frequency wavelet-domain deconvolution (FWDD) method and previous implementations of sparse deconvolution based on an iterative-shrinkage and thresholding algorithm (SD/IST), the proposed sparse-deconvolution approach can provide a clearer and rapid stratigraphic reconstruction of the paper stacks studied, while ensuring accurate thickness information for each paper sheet in the presence of noise, revealing the potential usage of real-time THz tomographic-image processing.

Published
2024
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20. Optical square waves in a semiconductor laser with nonlinear optoelectronic feedback

Author

Islam, M.S., Kovalev, A.V., Viktorov, E.A., Citrin, D.S., Locquet, A., School of Electrical and Computer Engineering - Georgia Insitute of Technology (ECE GeorgiaTech), Georgia Institute of Technology [Atlanta], National Research University of Information Technologies, Mechanics and Optics [St. Petersburg] (ITMO), Centre National de la Recherche Scientifique (CNRS), Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI]Engineering Sciences [physics], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

24. Structural characterization of mill-scale on production steel using terahertz pulse imaging in reflective geometry

Author

Zhai, Min, Locquet, A., Roquelet, Cyrielle, Citrin, D.S., Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS), and Locquet, Alexandre

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; Terahertz pulsed imaging was employed to characterize the mill scale thickness on production steel, validating this practical application of terahertz technology in a production environment.

Published
2020

25. Terahertz thickness measurement of multiple-layered coatings

Author

Zhai, Min, Locquet, A., Roquelet, Cyrielle, Citrin, D.S., Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS), and Locquet, Alexandre

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; Terahertz pulse reflectometry was employed to characterize the individual layers on metallic substrates. The autoregressive spectral extrapolation based on the modified covariance method was applied to enhance the axial resolution. All coating layers were resolved successfully and the calculated thickness of each layer based on deconvolved results shows a good agreement with the thickness value measured by eddy current technique, highlighting the promising application of terahertz technique on quality control among steel industries.

Published
2020

26. Characterization of nanoporous alumina using terahertz time domain reflectometry

Author

Zhai, Min, Locquet, A., Citrin, D.S., Locquet, Alexandre, Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; The nanoporous alumina films on Al substrates are characterized nondestructively by polarization-sensitive THz reflectometry. Sparse deconvolution is applied to estimate the film thickness, showing a good agreement with the value measured using the field emission scanning electron microscopes.

Published
2020

27. Electrooptic properties of InGaAsP asymmetric double quantum wells: enhanced slope efficiency in waveguide electroabsorption modulators

Author

Dong Kwon Kim and Citrin, D.S.

Subjects
Fiber optics -- Research, Gallium compounds -- Electric properties, Gallium compounds -- Optical properties, Quantum electronics -- Research, Fiber optics, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The theoretically estimated values of the various electrooptic properties of InGaAsP quantum well (EW) electroabsorption modulators (EAMs) are presented. The analysis suggests that the lowering of the operating bias voltage enhances the signal modulation efficiency of the system.

Published
2007

28. Optimized asymmetric double quantum well for high electric-field-sensitivity electroabsorption: excitonic mixing effects

Author

Dong Kwon Kim and Citrin, D.S.

Subjects
Electric fields -- Analysis, Quantum electronics -- Research, Exciton theory -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The paper presents the optimization of asymmetric double quantum wells (ADQWs) for getting maximum optical modulation sensitivity. It is seen that exciton mixing and states are important for getting such optimization.

Published
2007

29. Determination of the eigenfunctions of arbitrary nanostructures using time domain simulation

Author

Sullivan, Dennis M., Citrin, D.S., Williams, R. Stanley, Schroeder, J.L., and Meletis, E.I.

Subjects
Simulation methods -- Research, Eigenfunctions -- Research, Physics
Abstract

A simulation technique to determine the eigenfunctions for arbitrary nanostructures is demonstrated. This simulation based on the finite-difference time-domain method is very flexible.

Published
2002

34. Stepwise Radio Frequency Switching in a Semiconductor Laser with Optoelectronic Feedback

Author

Islam, Md Shariful, Coget, Grégoire, Kovalev, A.V., Viktorov, E.A., Citrin, D.S., Locquet, A., Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS), and Locquet, Alexandre

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; A step-like dependence in radio frequency is found in a semiconductor laser-based microwaveoscillator. The optoelectronic feedback is employed to yield periodic oscillation that displays sharp changesbetween the limit cycles when the feedback level is varied. Theoretical analysis provides evidence of a torusbifurcation leading to a transition between two coexisting attractors around these spectral switches. A detailedinvestigation manifests the presence of hysteresis in the switching sequence when the feedback level is rampedin the opposite direction.

Published
2019

35. Spectral Switches in Microwave Oscillation of Semiconductor Laser With Optoelectronic Feedback

Author

Islam, M.S., Coget, Grégoire, Kovalev, A.V., Locquet, A., Viktorov, E.A., Citrin, D.S., Georgia Tech Lorraine [Metz], Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Ecole Supérieure d'Electricité - SUPELEC (FRANCE)-Georgia Institute of Technology [Atlanta]-CentraleSupélec-Ecole Nationale Supérieure des Arts et Metiers Metz-Centre National de la Recherche Scientifique (CNRS), National Research University of Information Technologies, Mechanics and Optics [St. Petersburg] (ITMO), and Locquet, Alexandre

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics], [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; A semiconductor laser diode subject to optoelectronic feedback is found to exhibit discrete step-wise changes in the relaxation-oscillation frequency when the feedback level is gradually ramped up. The step-wise spectral changes between two limit cycles appear either as an abrupt shift or a progressive transition via a mediating quasiperiodic state. The switches are associated with subcritical Hopf bifurcation between two coexisting attractors as evidenced by the theoretical analysis. Further experimentalinquiry demonstrates the presence of hysteresis when the feedback level is ramped down.

Published
2019

36. Theory of gain in quantum-wire lasers grown in v-grooves

Author

Citrin, D.S. and Chang, Yia-Chung

Subjects
Semiconductor lasers -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The gain, refractive index difference, differential gain, temperature dependence of the gain and threshold current of GaAs-Al0.2Ga0.8As quantum-wire (QWR) lasers are numerically derived. The devices, which are products of V-grooves, are studied via the effective bond-orbital model which takes into consideration band-mixing, material anisotropy and other parameters. Results indicate an analogy between the QWR and quantum well lasers under room temperature operating conditions.

Published
1993

39. Quantum coherence in an optical modulator

Author

Carter, S.G., Birkedal, V., Wang, C.S., Coldren, L.A., Maslov, A.V., Citrin, D.S., and Sherwin, M.S.

Subjects
Quantum theory -- Research -- Analysis, Science and technology, Analysis, Research
Abstract

Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications., Quantum three-state systems in which two of the states are strongly coupled by an intense laser field have been widely studied in atomic and molecular systems (1). The energies of [...]

Published
2005

40. Intracavity nonlinearities in quantum-cascade lasers

Author

Bai, Jing and Citrin, D.S.

Subjects
Kerr effect -- Analysis, Laser beams -- Usage, Nonlinear optics -- Analysis, Quantum theory -- Analysis, Physics
Abstract

The article studies several intracavity optical nonlinearities up to the third order in quantum-cascade lasers. Findings suggest a simulation model accounting for nonlinear interactions in quantum-cascade lasers to evaluate the nonlinear performance.

Published
2009

41. Determining quantum eigenfunctions in three-dimensional nanoscale structures

Author

Sullivan, Dennis M. and Citrin, D.S.

Subjects
Nanotechnology -- Research, Schrodinger equation -- Research, Physics
Abstract

A method to solve the time-dependent Schrodinger equation that is capable of determining the eigenenergies and eignefunctions of arbitrary three-dimensional nanostructues is presented. This method is a formulation of the time-dependent Schrodinger equation into finite-difference time-domain method.

Published
2005

42. Time-domain simulation of a universal quantum gate

Author

Sullivan, Dennis M. and Citrin, D.S.

Subjects
Electron spin -- Analysis, Magnetic fields -- Analysis, Time-domain analysis, Physics
Abstract

The finite-difference time-domain (FDTD) method is discussed. The localized magnetic fields manipulating the target particle are described.

Published
2004

43. Quantum-well optical modulator at terahertz frequencies

Author

Maslov, A.V. and Citrin, D.S.

Subjects
Modulation (Electronics) -- Research, Terahertz radiation -- Research, Quantum wells -- Research, Physics
Abstract

The modulation index and contrast in terahertz (THz)-frequency quantum well (QW) optical modulators is calculated. The coherent nonlinear mixing of the optical and the THz-modulation fields leads to strong modification of the frequency dependence of the modulation depth.

Published
2003

44. Tunability in the Terahertz Regime: Charge-Carrier Wavepacket Manipulation in Quantum Wells

Author

Hughes, S. and Citrin, D.S.

Subjects
Wave packets -- Analysis, Quantum wells -- Analysis, Exciton theory -- Analysis, Astronomy, Physics
Abstract

A convenient method for generating upshifted and harmonically-generated terahertz transients via the creation of highly anisotropic electron-hole wavepackets in quantum wells is described. Our results are in agreement with experimental measurements.

Published
1999

45. LDPC-based secret key agreement over the Gaussian wiretap channel

Author

Locquet, A., Ortin, S., Udaltsov, V.S., Larger, L., Citrin, D.S, Pesquera, L., Valle, A., Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institute of Atomic Physics, Université de Roumanie, Laboratoire des sciences et matériaux pour l'électronique et d'automatique (LASMEA), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Key-agreement protocol, 021110 strategic, defence & security studies, Theoretical computer science, Gaussian, 0211 other engineering and technologies, 020206 networking & telecommunications, 02 engineering and technology, Data_CODINGANDINFORMATIONTHEORY, Cryptographic protocol, 16. Peace & justice, symbols.namesake, Additive white Gaussian noise, Secrecy, 0202 electrical engineering, electronic engineering, information engineering, symbols, Key (cryptography), [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, Low-density parity-check code, Computer Science::Information Theory, Computer Science::Cryptography and Security, Mathematics, Communication channel
Abstract

International audience; This paper investigates a practical secret key agreement protocol over the Gaussian wire-tap channel. The protocol is based on an efficient information reconciliation method which allows two parties having access to correlated continuous random variables to agree on a common bit string. We describe an explicit reconciliation method based on LDPC codes optimized with EXIT charts and density evolution. When used in conjunction with existing privacy amplification techniques our method allows secret key agreement over the Gaussian wire-tap channel close to the secrecy capacity

Published
2006

46. Time delay identification in chaotic cryptosystems ruled by delay– differential equations

Author

Udaltsov, V.S., Larger, L., Goedgebuer, J.P., Locquet, A., Citrin, D.S., Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Laboratoire des sciences et matériaux pour l'électronique et d'automatique (LASMEA), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)

Published
2005

47. Some aspects of security of chaos–based communications

Author

Udaltsov, V.S, Locquet, A., Larger, L., Goedgebuer, J.-P., Citrin, D.S, Institute of Atomic Physics, Université de Roumanie, Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)

Published
2005

48. Delay time identification in chaotic cryptosystems with two delayed feedback loops

Author

Locquet, A., Udaltsov, V.S, Larger, L., Citrin, D.S, Goedgebuer, J.-P., Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS), Institute of Atomic Physics, and Université de Roumanie

Published
2005

49. Carrier capture processes in strain-induced InxGa1-xAs/GaAs quantum dot structures

Author

Lingk, C., Helfer, W., von Plessen, G., Feldmann, J., Stock, K., Feise, W.M., Citrin, D.S., Lipsanen, H., Sopanen, M., Virkkala, R., Tulkki, J., Ahopelto, J., Sähkötekniikan korkeakoulu, School of Electrical Engineering, Department of Micro and Nanosciences, Mikro- ja nanotekniikan laitos, Aalto-yliopisto, Aalto University, and Department of Neuroscience and Biomedical Engineering

Subjects
Condensed Matter::Materials Science, quantum wells, photoluminescence spectroscopy, Physics, technology, industry, and agriculture, carrier capture processes, quantum dot, stressor, photoluminescence, quantum dots, equipment and supplies, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

We investigate carrier capture processes in strain-induced quantum dot structures. The quantum dots consist of a near-surface InGaAs/GaAs quantum well in which a lateral confining potential is generated by the strain from InP stressor islands grown on the sample surface. Using photoluminescence spectroscopy, we show that the rate of carrier capture into the quantum dots increases dramatically when the energetic depth of the confinement potential is reduced by enlarging the quantum well/surface separation D. While carriers in the quantum well region between the quantum dots are found to experience D-dependent nonradiative surface recombination, this process seems to be negligible for carriers in the quantum dots, presumably due to the protecting InP islands.

Published
2000

50. Coherent exciton-photon dynamics in single, double, and quintuple quantum wells

Author

Weber, D., Feldmann, J., Göbel, E.O., Citrin, D.S., Köhler, K., and Publica

Subjects
III-V semiconductors, quantum wells, time resolved electrical measurement, zeitaufgelöste Messung, heterostructure, III-V Halbleiter, Heterostruktur
Abstract

We have studied experimentally the coherent exciton-photon dynamics in a single, a double, and a quintuple quantum well structure under resonant excitation. In pump and probe experiments we observe an initial fast decay of the exciton population. This initial decay depends on the number of quantum wells. The population decay is accompanied by a coherent light emission induced by the first-order polarization, the intensity of which increases quadratically with the quantum well number. Interference effects and electromagnetic coupling effects between polarizations located in distinct quantum wells probably play a crucial role in the superlinear coherent emission process.

Published
1995

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