Optimization and selection of time-frequency transforms for wave-packet analysis in ultrafast spectroscopy

Volpato, Andrea; Collini, Elisabetta

doi:10.1364/oe.27.002975

Cited by 15 publications

(22 citation statements)

References 36 publications

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“…The observed coherent dynamics, the real focus of this work, has been analyzed using both global fitting techniques and time-frequency transform (TFT) analysis of traces extracted at relevant coordinates. 31,32 In the regions of the 2D map in the proximity of the diagonal-peak ( Figures 2(b, d)), the oscillating dynamics is dominated by the longitudinal optical (LO) phonon with a beating frequency of about 200 cm -1 , whose presence has been already characterized in several CdSe QDs samples. 24,27,30,33,34 The dephasing dynamics of this phonon mode and its coupling with electronic degrees of freedom has been the focus of several theoretical and experimental investigations, and it is still under scrutiny.…”

Section: )mentioning

confidence: 79%

“…29 and time-frequency transform analysis. 31,32 The stability of the samples under laser excitation has been tested collecting iteratively 2DES spectra at two values of t2 (50 and 200 fs) for 995 times, corresponding to a total elapsed time of about 4000 minutes (3 days), in the same experimental conditions described before. All the measurements have been done on the same spot of the sample.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Collini

Gattuso²,

Kolodny³

et al. 2020

Preprint

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<div><div><div><p>The full blossoming of quantum technologies requires the availability of easy-to-prepare materials where quantum coherences can be effectively initiated, controlled and exploited, preferably at ambient conditions. Solid-state multilayers of colloidally grown quantum dots (QDs) are highly promising for this task because of the possibility of assembling networks of electronically coupled QDs through the modulation of sizes, inter-dot linkers and distances. To usefully probe coherence in these materials, the dynamical characterization of their collective quantum mechanically coupled states is needed. Here we explore by 2D electronic spectroscopy the coherent dynamics of solid-state multilayers of electronically coupled colloidally grown CdSe QDs and complement it by detailed computations. The time evolution of a coherent superposition of states delocalized over more than one QD was captured at ambient conditions. We thus provide important evidence for inter-dot coherences in such solid-state materials, opening up the effective exploitation of these materials towards quantum technologies.</p></div></div></div>

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Section: )mentioning

confidence: 79%

Section: Experimental Methodsmentioning

confidence: 99%

Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Collini

Gattuso²,

Kolodny³

et al. 2020

Preprint

Self Cite

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“…In particular, we use a smoothed pseudo-Wigner-Ville (SPWV) time-frequency transform which has been shown to more accurately reproduce time-resolved oscillations with exceptional frequency-and timeresolution and minimal artifacts (for further explanation see section S3 the Supplementary Information). [45][46][47] We show in Figure 2C the SPWV transform spectrum of the transient reflectivity oscillations which correspond to the Fourier transform power spectra. This spectrum reveals two coherent phonons with frequencies around 50 cm -1 and 90 cm -1 that exhibit time-dependent frequency shifts.…”

Section: Resultsmentioning

confidence: 97%

Coherent Phonon Catalysts: Lattice Vibrations Drive a Photoinduced Phase Transition in a Molecular Crystal

Rich

Frontiera

2020

Preprint

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The atomic motions that make up phonons and molecular vibrations in molecular crystals influence their photophysical and electronic properties including polaron formation, carrier mobility, and phase transitions. Discriminating between spectator and driving motions is a significant challenge hindering optimization. Unlocking this information and developing fine-tuned controls over actively participating phonon modes would not only lead to a stronger understanding of photochemistry but also provide a significant new tool in controlling solid-state chemistry. We present a strategy using rationally-designed double pulses to enhance the yield of a photoinduced phase transition in a molecular crystal through coherent control of individual phonons. Using ultrafast spectroscopy, we identified 50 cm<sup>-1</sup> and 90 cm<sup>-1</sup> phonons responsible for the photoinduced spin-Peierls melting of potassium tetracyanoquinodimethane crystals. We show that the 90 cm<sup>-1</sup> phonon can be used to catalyze the phase transition process while the 50 cm<sup>-1</sup> phonon enhances the yield of the initial charge transfer reaction.<br>

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“…These phenomena can complicate the interpretation of the representation by overlapping the signal components or producing negative values. Nevertheless, bilinear representations generally exhibit improved TF concentration and resolution, despite the interference terms being introduced [ 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

Entropy-Based Concentration and Instantaneous Frequency of TFDs from Cohen’s, Affine, and Reassigned Classes

Bačnar

Saulig

Vuksanović

et al. 2022

Sensors

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This paper explores three groups of time–frequency distributions: the Cohen’s, affine, and reassigned classes of time–frequency representations (TFRs). This study provides detailed insight into the theory behind the selected TFRs belonging to these classes. Extensive numerical simulations were performed with examples that illustrate the behavior of the analyzed TFR classes in the joint time–frequency domain. The methods were applied both on synthetic and real-life non-stationary signals. The obtained results were assessed with respect to time–frequency concentration (measured by the Rényi entropy), instantaneous frequency (IF) estimation accuracy, cross-term presence in the TFRs, and the computational cost of the TFRs. This study gives valuable insight into the advantages and limitations of the analyzed TFRs and assists in selecting the proper distribution when analyzing given non-stationary signals in the time–frequency domain.

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Optimization and selection of time-frequency transforms for wave-packet analysis in ultrafast spectroscopy

Cited by 15 publications

References 36 publications

Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Room Temperature Inter-Dot Coherent Dynamics in Multilayers Quantum Dot Materials

Coherent Phonon Catalysts: Lattice Vibrations Drive a Photoinduced Phase Transition in a Molecular Crystal

Entropy-Based Concentration and Instantaneous Frequency of TFDs from Cohen’s, Affine, and Reassigned Classes

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