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Andrea Cavalleri - One of the best experts on this subject based on the ideXlab platform.

  • Coherent Modulation of the YBa2Cu3O6+x atomic structure by displacive stimulated ionic Raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian

  • Coherent Modulation of the yba2cu3o6 x atomic structure by displacive stimulated ionic raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian

Roman Mankowsky - One of the best experts on this subject based on the ideXlab platform.

  • Coherent Modulation of the YBa2Cu3O6+x atomic structure by displacive stimulated ionic Raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian

  • Coherent Modulation of the yba2cu3o6 x atomic structure by displacive stimulated ionic raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian

Les Atlas - One of the best experts on this subject based on the ideXlab platform.

  • time frequency Coherent Modulation filtering of nonstationary signals
    IEEE Transactions on Signal Processing, 2009
    Co-Authors: P Clark, Les Atlas
    Abstract:

    Modulation filtering is a class of techniques for filtering slowly-varying Modulation envelopes of frequency subbands of a signal, ideally without affecting the subband signal's temporal fine-structure. Coherent Modulation filtering is a potentially more effective type of such techniques where, via an explicit product model, subband envelopes are determined from deModulation of the subband signal with a Coherently detected subband carrier. In this paper we propose a Coherent Modulation filtering technique based on detecting the instantaneous frequency of a subband from its time-frequency representation. We devise theory to show that Coherent Modulation filtering imposes a new bandlimiting constraint on the product of the modulator and carrier as well as the ability to recover arbitrarily chosen envelopes and carriers from their Modulation product. We then formally show that a carrier estimate based on the time-varying spectral center-of-gravity satisfies the bandlimiting condition. This bandwidth constraint leads to effective and artifact-free Modulation filters, offering new approaches for potential signal modification. However, the spectral center-of-gravity does not, in general, satisfy the condition of arbitrary carrier recovery. Finally, the results from Modulation-filtering a speech signal are then used to validate the theory.

  • ICASSP - A sum-of-products model for effective Coherent Modulation filtering
    2009 IEEE International Conference on Acoustics Speech and Signal Processing, 2009
    Co-Authors: P Clark, Les Atlas
    Abstract:

    Modulation filtering is a technique for filtering slowly-varying envelopes of frequency subbands of a nonstationary signal, ideally without affecting the signal's phase and fine-structure. Coherent Modulation filtering is a promising subtype of such techniques where subband envelopes are determined through deModulation of the subband signal with a Coherently detected subband carrier. In this paper we demonstrate how Modulation filtering, when done Coherently, is far more effective than standard inCoherent methods. We show that empirical results can be made to be almost ideal, and significantly better than previous Coherent attempts, as long as fine-structure information is retained as side information and the filterbank reduces subband interference.

  • Improving performance in noise for hearing aids and cochlear implants using Coherent Modulation filtering.
    Hearing Research, 2008
    Co-Authors: Jong Ho Won, Les Atlas, Steven M. Schimmel, Ward R. Drennan, Pamela E. Souza, Jay T. Rubinstein
    Abstract:

    This study evaluated the maximal attainable performance of speech enhancement strategies based on Coherent Modulation filtering. An optimal adaptive Coherent Modulation filtering algorithm was designed to enhance known signals from a target talker in two-talker babble noise. The algorithm was evaluated in a closed-set, speech-recognition-in-noise task. The speech reception threshold (SRT) was measured using a one-down, one-up adaptive procedure. Five hearing-impaired subjects and five cochlear implant users were tested in three processing conditions: (1) original sounds; (2) fixed Coherent Modulation filtered sounds; and (3) optimal Coherent Modulation filtered sounds. Six normal-hearing subjects were tested with a 6-channel cochlear implant simulation of sounds processed in the same three conditions. Significant improvements in SRTs were observed when the signal was processed with the optimal Coherent Modulation filtering algorithm. There was no benefit when the signal was processed with the fixed Modulation filter. The current study suggested that Coherent Modulation filtering might be a promising method for front-end processing in hearing aids and cochlear implants. An approach such as hidden Markov models could be used to generalize the optimal Coherent Modulation filtering algorithm to unknown utterances and to extend it to open-set speech.

  • ICASSP - Coherent Modulation filtering for speech
    2008 IEEE International Conference on Acoustics Speech and Signal Processing, 2008
    Co-Authors: Les Atlas
    Abstract:

    Modulation filtering ideally offers a new approach to modifying the dynamics of non-stationary signals, such as speech. In this paper, a new type of Coherent Modulation analysis and filtering method is proposed. The new method consists of two essential parts - an instantaneous frequency estimator based on conditional mean frequency, which is used for Coherent Modulation analysis, and a multi-component decomposition based on spectrogram peak tracking, which is used to separate multiple Modulation components in signals. An important Modulation filtering property, frequency shift invariance, is achieved with the new proposed method.

  • ICASSP - Target talker enhancement in hearing devices
    2008 IEEE International Conference on Acoustics Speech and Signal Processing, 2008
    Co-Authors: Steven M. Schimmel, Les Atlas
    Abstract:

    We describe a novel Coherent Modulation filtering technique for single channel target talker enhancement in the presence of interfering talkers. For this technique, we have expanded our previous work on Coherent Modulation filtering with a carrier estimator that is more robust to speech from interfering talkers, and a Modulation filter that operates on shorter time-scales. We have evaluated the technique in a subjective listening test, which indicates that the novel target talker enhancement technique achieves a moderate improvement in speech reception. We summarize our observations on single channel target talker enhancement and conclude with directions for further research.

Liantuan Xiao - One of the best experts on this subject based on the ideXlab platform.

  • Visualizing Quantum Coherence Based on Single-Molecule Coherent Modulation Microscopy.
    Nano letters, 2021
    Co-Authors: Haitao Zhou, Chengbing Qin, Ruiyun Chen, Yaoming Liu, Guofeng Zhang, Shuangping Han, Lei Zhang, Liantuan Xiao
    Abstract:

    Massive magical phenomena in nature are closely related to quantum effects at the microscopic scale. However, the lack of straightforward methods to observe the quantum Coherent dynamics in integrated biological systems limits the study of essential biological mechanisms. In this work, we developed a single-molecule Coherent Modulation (SMCM) microscopy by combining the superior features of single-molecule microscopy with ultrafast spectroscopy. By introducing the modem technology and defining the Coherent visibility, we realized visualization and real-time observation of the decoherence process of a single molecule influenced by the microenvironment for the first time. In particular, we applied this technique to observe the quantum Coherent properties of the entire chlorella cells and found the correlation between the Coherent visibility and metabolic activities, which may have potential applications in molecular diagnostics and precision medicine.

  • Quantum Coherent Modulation-Enhanced Single-Molecule Imaging Microscopy.
    The journal of physical chemistry letters, 2019
    Co-Authors: Haitao Zhou, Chengbing Qin, Ruiyun Chen, Yaoming Liu, Wenjin Zhou, Guofeng Zhang, Yan Gao, Liantuan Xiao, Suotang Jia
    Abstract:

    In fluorescence imaging and detection, undesired fluorescence interference (such as autofluorescence) often hampers the contrast of the image and even prevents the identification of structures of interest. Here, we develop a quantum Coherent Modulation-enhanced (QCME) single-molecule imaging microscopy (SMIM) to substantially eliminate the strong fluorescence interference, based on manipulation of the excited-state population probability of a single molecule. By periodically modulating the phase difference between the ultrashort pulse pairs and performing a discrete Fourier transform of the arrival time of emitted photons, the decimation of single molecules from strong interference in QCME-SMIM has been clearly determined, where the signal-to-interference ratio is enhanced by more than 2 orders of magnitude. This technique, confirmed to be universal to organic dyes and linked with biomacromolecules, paves the way to high-contrast bioimaging under unfavorable conditions.

Michael Först - One of the best experts on this subject based on the ideXlab platform.

  • Coherent Modulation of the YBa2Cu3O6+x atomic structure by displacive stimulated ionic Raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian

  • Coherent Modulation of the yba2cu3o6 x atomic structure by displacive stimulated ionic raman scattering
    Physical Review B, 2015
    Co-Authors: Roman Mankowsky, Michael Först, Toshinao Loew, Juan Porras, Bernhard Keimer, Andrea Cavalleri
    Abstract:

    Midinfrared light pulses can be used to resonantly excite optically active lattice vibrations in solids to amplitudes as high as several percent of interatomic distances. This technique has been shown to induce changes in the collective magnetic and electronic properties of many materials [1–3]. Integral to this optical control mechanism is the anharmonic coupling between the directly driven, optically active mode and other lattice vibrations [4–6]. The coupling is typically dominated by cubic anharmonicities and involves a displacive force that acts onto the crystal lattice in two ways. First, a phononic analog to rectification in nonlinear optics causes a quasistatic displacement along the normal mode coordinates of all coupled Raman modes. Secondly, whenever the displacive force rises promptly compared to the period of any of the anharmonically coupled modes, Coherent oscillatory motions of these modes are excited. This second effect is the stimulated equivalent of ionic Raman scattering. Here, we study the Coherent optical response of YBa2Cu3O6+x. Infrared-active apical oxygen motions are driven resonantly with midinfrared pulses at 20 THz, under the conditions for which superconducting transport is transiently enhanced [7–9]. We find that for excitation with pulses of 140 fs duration, for which only modes with frequency < 6T Hz can be driven Coherently, oscillations of four Raman modes are stimulated, involving displacements of the copper atoms along the crystallographic c axis. This motion induces periodic changes in the in-plane O-Cu bond buckling and leads to an oscillatory transfer of charges between the CuO2 planes and the Cu-O chains [9], effectively modifying the doping of the planes; an effect that may be part of the puzzle of optically enhanced superconductivity in this compound [7–9]. We next discuss the process of stimulated ionic Raman scattering in more detail. The indirect excitation of Coherent Raman modes by resonant excitation of large amplitude infrared-active (IR) vibrations in a solid is described to lowest order by the lattice Hamiltonian