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Steven T. Cundiff - One of the best experts on this subject based on the ideXlab platform.
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Pulse Propagation Effects in Optical 2d Fourier-Transform Spectroscopy: Theory.
The journal of physical chemistry. A, 2015Co-Authors: Steven T. Cundiff, Austin P. Spencer, David M. JonasAbstract:A solution to Maxwell’s equations in the three-dimensional frequency domain is used to calculate rephasing two-dimensional Fourier Transform (2dFT) spectra of the D2 line of atomic rubidium vapor in argon buffer gas. Experimental distortions from the spatial propagation of pulses through the sample are simulated in 2dFT spectra calculated for the homogeneous Bloch line shape model. Spectral features that appear at optical densities of up to 3 are investigated. As optical density increases, absorptive and dispersive distortions start with peak shape broadening, progress to peak splitting, and ultimately result in a previously unexplored coherent transient twisting of the split peaks. In contrast to the low optical density limit, where the 2d peak shape for the Bloch model depends only on the total dephasing time, these distortions of the 2d peak shape at finite optical density vary with the waiting time and the excited state lifetime through coherent transient effects. Experiment-specific conditions are ex...
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Pulse Propagation Effects in Optical 2d Fourier-Transform Spectroscopy: Experiment
The journal of physical chemistry. A, 2013Co-Authors: Austin P. Spencer, Galan Moody, David M. Jonas, Andrew Kortyna, Steven T. CundiffAbstract:In optical two-dimensional Fourier-Transform (2dFT) spectroscopy, understanding how the spectral line shape is affected by pulse propagation in the sample is crucial for an accurate interpretation of spectra. We report an experimental study of pulse propagation effects in 2dFT spectroscopy performed in a dense atomic vapor. The spectral line shape can be dramatically distorted due to high optical density as well as the physical thickness of a sample. The spectral distortion can be partially corrected by using a reference pulse copropagating with the signal combined with appropriate data processing.
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Coupling in InGaAs double quantum wells studied with 2d Fourier Transform spectroscopy
CLEO: 2013, 2013Co-Authors: Gaël Nardin, Galan Moody, Rohan Singh, Travis M. Autry, François Morier-genoud, Steven T. CundiffAbstract:We study asymmetric double InGaAs quantum well samples, featuring three different barrier widths, using optical two-dimensional Fourier Transform spectroscopy. Depending on the barrier width, we observe different coupling mechanisms between the two wells.
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revealing exciton dephasing and transport dynamics in semiconductor quantum well quantum dot systems using optical 2d Fourier Transform spectroscopy
Proceedings of SPIE, 2012Co-Authors: D. Karaiskaj, Alan D. Bristow, Daniel Gammon, Allan S. Bracker, Steven T. Cundiff, Xingcan Dai, Galan Moody, Mark E SiemensAbstract:Exciton dephasing and relaxation dynamics are studied in a GaAs quantum dot ensemble using optical twodimensional Fourier Transform spectroscopy. We measure the temperature and excitation-density dependence of the exciton ground-state homogeneous lineshape of quantum dots within the ensemble and show that acoustic phonon sidebands are absent. The linewidth increases nonlinearly with temperature from 6 to 50 K and the behavior is well-described by an Arrhenius equation with an offset. The absence of a phonon-activation peak in the spectra reveals that elastic exciton-phonon scattering is the primary dephasing mechanism and the results can be explained qualitatively using an extension of the independent Boson model that includes quadratic coupling in the phonon displacement coordinates. At temperatures ≥ 35 K, spectral features associated with phonon-assisted population transfer of excitons out of the quantum dots and into quantum wells states begin to appear.
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Excitons, biexcitons, and trions in an InAs quantum dot ensemble studied with 2d Fourier-Transform spectroscopy
Conference on Lasers and Electro-Optics 2012, 2012Co-Authors: Galan Moody, Rohan Singh, I. A. Akimov, Manfred Bayer, Dirk Reuter, Andreas D. Wieck, Steven T. CundiffAbstract:Multi-particle correlations are investigated in an InAs quantum dot ensemble using 2d Fourier-Transform spectroscopy. Signatures of trions and a fifth-order contribution from the biexciton are observed by varying the excitation polarization and density.
Keith A. Nelson - One of the best experts on this subject based on the ideXlab platform.
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Selective enhancements in 2d Fourier Transform optical spectroscopy with tailored pulse shapes.
The journal of physical chemistry. A, 2013Co-Authors: Patrick Y. Wen, Keith A. NelsonAbstract:Spectral features in two-dimensional Fourier Transform optical spectroscopy were selectively enhanced using pulse shapes and sequences designed to amplify specific excited-state resonances. The enhancement was achieved by tailoring a small set of input parameters that control the amplitude and phase profiles of the excitation fields, coherently driving or suppressing selected resonances. The tailored pulse shapes were applied to enhance exciton and biexciton coherences in a semiconductor quantum well. Enhancement of selected resonances was demonstrated even in cases of spectrally overlapping features and complex many-body interactions. Modifications in the 2d spectral line shapes due to the tailored waveforms were calculated using the optical Bloch equations.
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Selective Excitation of Resonances in 2d Fourier Transform Optical Spectroscopy with Tailored Pulse Shapes
International Conference on Ultrafast Phenomena, 2010Co-Authors: Keith A. Nelson, Patrick Y. Wen, Dylan H. Arias, Daniel B. TurnerAbstract:Shaped pulses, with phase windows and double amplitudes, are tailored for specific resonances in 2-D Fourier Transform optical spectroscopy. Pulses, designed using Feynman pathway analysis, selectively enhance biexciton peaks in 2-D spectra of quantum wells.
Galan Moody - One of the best experts on this subject based on the ideXlab platform.
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Pulse Propagation Effects in Optical 2d Fourier-Transform Spectroscopy: Experiment
The journal of physical chemistry. A, 2013Co-Authors: Austin P. Spencer, Galan Moody, David M. Jonas, Andrew Kortyna, Steven T. CundiffAbstract:In optical two-dimensional Fourier-Transform (2dFT) spectroscopy, understanding how the spectral line shape is affected by pulse propagation in the sample is crucial for an accurate interpretation of spectra. We report an experimental study of pulse propagation effects in 2dFT spectroscopy performed in a dense atomic vapor. The spectral line shape can be dramatically distorted due to high optical density as well as the physical thickness of a sample. The spectral distortion can be partially corrected by using a reference pulse copropagating with the signal combined with appropriate data processing.
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Coupling in InGaAs double quantum wells studied with 2d Fourier Transform spectroscopy
CLEO: 2013, 2013Co-Authors: Gaël Nardin, Galan Moody, Rohan Singh, Travis M. Autry, François Morier-genoud, Steven T. CundiffAbstract:We study asymmetric double InGaAs quantum well samples, featuring three different barrier widths, using optical two-dimensional Fourier Transform spectroscopy. Depending on the barrier width, we observe different coupling mechanisms between the two wells.
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revealing exciton dephasing and transport dynamics in semiconductor quantum well quantum dot systems using optical 2d Fourier Transform spectroscopy
Proceedings of SPIE, 2012Co-Authors: D. Karaiskaj, Alan D. Bristow, Daniel Gammon, Allan S. Bracker, Steven T. Cundiff, Xingcan Dai, Galan Moody, Mark E SiemensAbstract:Exciton dephasing and relaxation dynamics are studied in a GaAs quantum dot ensemble using optical twodimensional Fourier Transform spectroscopy. We measure the temperature and excitation-density dependence of the exciton ground-state homogeneous lineshape of quantum dots within the ensemble and show that acoustic phonon sidebands are absent. The linewidth increases nonlinearly with temperature from 6 to 50 K and the behavior is well-described by an Arrhenius equation with an offset. The absence of a phonon-activation peak in the spectra reveals that elastic exciton-phonon scattering is the primary dephasing mechanism and the results can be explained qualitatively using an extension of the independent Boson model that includes quadratic coupling in the phonon displacement coordinates. At temperatures ≥ 35 K, spectral features associated with phonon-assisted population transfer of excitons out of the quantum dots and into quantum wells states begin to appear.
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Excitons, biexcitons, and trions in an InAs quantum dot ensemble studied with 2d Fourier-Transform spectroscopy
Conference on Lasers and Electro-Optics 2012, 2012Co-Authors: Galan Moody, Rohan Singh, I. A. Akimov, Manfred Bayer, Dirk Reuter, Andreas D. Wieck, Steven T. CundiffAbstract:Multi-particle correlations are investigated in an InAs quantum dot ensemble using 2d Fourier-Transform spectroscopy. Signatures of trions and a fifth-order contribution from the biexciton are observed by varying the excitation polarization and density.
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Coherence of fine-structure states of an InAs quantum dot ensemble studied with 2d Fourier-Transform spectroscopy
Conference on Lasers and Electro-Optics 2012, 2012Co-Authors: Rohan Singh, Galan Moody, I. A. Akimov, Manfred Bayer, Dirk Reuter, Andreas D. Wieck, Steven T. CundiffAbstract:Coherence decay times of and between fine-structure states is obtained from an InAs quantum dot ensemble using optical 2d Fourier-Transform spectroscopy. This technique allows us to investigate properties of QDs within the ensemble.
David M. Jonas - One of the best experts on this subject based on the ideXlab platform.
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Pulse Propagation Effects in Optical 2d Fourier-Transform Spectroscopy: Theory.
The journal of physical chemistry. A, 2015Co-Authors: Steven T. Cundiff, Austin P. Spencer, David M. JonasAbstract:A solution to Maxwell’s equations in the three-dimensional frequency domain is used to calculate rephasing two-dimensional Fourier Transform (2dFT) spectra of the D2 line of atomic rubidium vapor in argon buffer gas. Experimental distortions from the spatial propagation of pulses through the sample are simulated in 2dFT spectra calculated for the homogeneous Bloch line shape model. Spectral features that appear at optical densities of up to 3 are investigated. As optical density increases, absorptive and dispersive distortions start with peak shape broadening, progress to peak splitting, and ultimately result in a previously unexplored coherent transient twisting of the split peaks. In contrast to the low optical density limit, where the 2d peak shape for the Bloch model depends only on the total dephasing time, these distortions of the 2d peak shape at finite optical density vary with the waiting time and the excited state lifetime through coherent transient effects. Experiment-specific conditions are ex...
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Pulse Propagation Effects in Optical 2d Fourier-Transform Spectroscopy: Experiment
The journal of physical chemistry. A, 2013Co-Authors: Austin P. Spencer, Galan Moody, David M. Jonas, Andrew Kortyna, Steven T. CundiffAbstract:In optical two-dimensional Fourier-Transform (2dFT) spectroscopy, understanding how the spectral line shape is affected by pulse propagation in the sample is crucial for an accurate interpretation of spectra. We report an experimental study of pulse propagation effects in 2dFT spectroscopy performed in a dense atomic vapor. The spectral line shape can be dramatically distorted due to high optical density as well as the physical thickness of a sample. The spectral distortion can be partially corrected by using a reference pulse copropagating with the signal combined with appropriate data processing.
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Propagation and beam geometry effects on 2d Fourier Transform spectra of multi-level systems
Springer Series in Chemical Physics, 2009Co-Authors: Byungmoon Cho, Michael K. Yetzbacher, Katherine A. Kitney, Eric R. Smith, David M. JonasAbstract:We calculate 4-level two-dimensional (2d) Fourier Transform relaxation spectra with propagation and beam geometry distortions, which are 14% for an optical density of 0.2 and 25% for a crossing angle of 10°.
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two dimensional femtosecond spectroscopy
Annual Review of Physical Chemistry, 2003Co-Authors: David M. JonasAbstract:▪ Abstract The simplest two-dimensional (2d) spectra show how excitation with one (variable) frequency affects the spectrum at all other frequencies, thus revealing the molecular connections between transitions. Femtosecond 2d Fourier Transform (2d FT) spectra are more flexible and share some of the remarkable properties of their conceptual parent, 2d FT nuclear magnetic resonance. When 2d FT spectra are experimentally separated into real absorptive and imaginary refractive parts, the time resolution and frequency resolution can both reach the uncertainty limit set for each resonance by the sample itself. Coherent four-level contributions to the signal provide new molecular phase information, such as relative signs of transition dipoles. The nonlinear response can be picked apart by selecting a single coherence pathway (e.g., specifying the relative signs of energy level difference frequencies during different time intervals as in the photon echo). Because molecules are frozen on the femtosecond timescale...
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Polar and non-polar solvation in the femtosecond evolution of 2d Fourier Transform spectra
The Thirteenth International Conference on Ultrafast Phenomena, 2002Co-Authors: David M. Jonas, John D. Hybl, Darcie A. FarrowAbstract:A combination of magic angle pump-probe and femtosecond 2d Fourier Transform spectra is used to probe polar and non-polar solvation in two structurally related molecules with and without a dipole moment change upon electronic excitation.
Albert Macovski - One of the best experts on this subject based on the ideXlab platform.
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deblurring for non 2d Fourier Transform magnetic resonance imaging
Magnetic Resonance in Medicine, 1992Co-Authors: Douglas C. Noll, John M. Pauly, Craig H. Meyer, Dwight G. Nishimura, Albert MacovskiAbstract:For several non-2d Fourier Transform imaging methods, off-resonant reconstruction does not just cause geometric distortion, but changes the shape of the point spread function and causes blurring. This effect is well known for projection reconstruction and spiral k-space scanning sequences. We introduce here a method that automatically removes blur introduced by magnetic field inhomogeneity and susceptibility without using a resonant frequency map, making these imaging methods more useful. In this method, the raw data are modulated to several different frequencies and reconstructed to create a series of base images. Determination of degree of blur is done by calculating a focusing measure for each point in each base image and a composite image is then constructed using only the unblurred regions from each base image. This method has been successfully applied to phantom and in vivo images using projection-reconstruction and spiral-scan sequences.
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Deblurring for non-2d Fourier Transform magnetic resonance imaging.
Magnetic resonance in medicine, 1992Co-Authors: Douglas C. Noll, John M. Pauly, Craig H. Meyer, Dwight G. Nishimura, Albert MacovskiAbstract:For several non-2d Fourier Transform imaging methods, off-resonant reconstruction does not just cause geometric distortion, but changes the shape of the point spread function and causes blurring. This effect is well known for projection reconstruction and spiral k-space scanning sequences. We introduce here a method that automatically removes blur introduced by magnetic field inhomogeneity and susceptibility without using a resonant frequency map, making these imaging methods more useful. In this method, the raw data are modulated to several different frequencies and reconstructed to create a series of base images. Determination of degree of blur is done by calculating a focusing measure for each point in each base image and a composite image is then constructed using only the unblurred regions from each base image. This method has been successfully applied to phantom and in vivo images using projection-reconstruction and spiral-scan sequences. © 1992 Academic Press, Inc.