Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J. R.; Krenner, Hubert J.; Wixforth, Achim; Salditt, Tim

doi:10.1107/s1600576714016896

Cited by 12 publications

(12 citation statements)

References 38 publications

(30 reference statements)

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“…Subsequently we observe oscillations of the diffracted intensity with a period of T SAW = 1310 ps. Due to the short x-ray penetration depth in our surface diffraction experiment, we rely on kinematic theory [31][32][33][34] and find the following expression for the diffracted intensity from a PSE under grazing incidence below the critical angle α i < α c :…”

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confidence: 99%

Spatiotemporal Coherent Control of Thermal Excitations in Solids

et al. 2017

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X-ray reflectivity (XRR) measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatio-temporal coherent control of thermally induced surface deformations on ultrafast timescales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-Å resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period Λ can be canceled by a second, time-delayed TG excitation shifted by Λ/2. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments. [5][6][7] or plasmonic [8,9] degrees of freedom. Strain-induced phenomena may be used to discover new material properties and develop new applications, for example the modification of optical and electronic properties in semiconductor nanostructures [10]. Surface acoustic waves (SAWs) are often employed as a source of lattice strain. They can be generated [11] and controlled [12] optically via the excitation of transient gratings (TGs) [13,14]. Recently, these TG-excitations heave been used to probe heat transport in suspended thin films [15] and magneto-elastic coupling in thin nickel films [16][17][18]. Optical excitation of a solid generates not only coherent sound waves but also incoherent thermal strain. Coherent excitations can be controlled in amplitude and phase by series of light pulses in time domain, which is labeled temporal coherent control [19]. The main fraction of the deposited optical energy is stored in incoherent excitations of the lattice, i.e., heat [20,21] which can consequently not be controlled by a temporal sequence of light pulses. This thermal lattice excitation often generates a background which makes is difficult to precisely observe the coherent acoustic signal in purely optical experiments.In this letter we demonstrate, for the first time, the coherent control of incoherent, thermal transient gratings. We apply spatio-temporal coherent control showing that the spatial part of coherent control adds a new degree of freedom to control the amplitude and the phase of a thermally deformed surface. This is clearly a new approach that introduces the concept of spatial coherent control to the dynamics of incoherent excitations on ultrafast time scales, a phenomenon impossible to achieve with temporal coherent control only. We also demonstrate the control of a transient thermal grating on a timescale faster than the oscillation of the simultaneously excited coherent acoustic modes. Our new quantitative method allows for decomposing the coherent and incoherent dynamics in the sample by measuring the amplitude of the surface excursion with sub-Å precision and ≈ 70 ps temporal resolution. The modification of x-ray diffracti...

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confidence: 99%

Spatiotemporal Coherent Control of Thermal Excitations in Solids

et al. 2017

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“…Typically, experiments employ an optical laser pulse which is diffracted from the excited modes via photothermal or photoelastic effects [28,29]. Alternatively, PSDs can be detected using x-ray diffraction and photoemission electron microscopy techniques [30][31][32]. We have recently shown that the PSD associated with the excited quasi-static and transient modes may also be probed by TR-XRR [14,15].…”

Section: Coherent Control Of Periodic Surface Deformationsmentioning

confidence: 99%

Full Spatiotemporal Control of Laser-Excited Periodic Surface Deformations

et al. 2019

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We demonstrate full control of acoustic and thermal periodic deformations at solid surfaces down to sub-nanosecond time scales and few-micrometer length scales via independent variation of the temporal and spatial phase of two optical transient grating (TG) excitations. For this purpose, we introduce an experimental setup that exerts control of the spatial phase of subsequent time-delayed TG excitations depending on their polarization state. Specific exemplary coherent control cases are discussed theoretically and corresponding experimental data are presented in which time-resolved x-ray reflectivity measures the spatiotemporal surface distortion of nanolayered heterostructures. Finally, we discuss examples where the application of our method may enable the control of functional material properties via tailored spatiotemporal strain fields.

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“…Surface acoustic waves (SAWs) have been previously observed with frequency-matched synchrotron X-ray scattering, historically with diffraction micro-topography [18,19], more recently with iterative phase retrieval of surface topography utilizing SAW satellite peaks [20,21], and also with photoemission electron microscopy tech-niques [22,23]. These methods have typically utilized full field x-ray illumination with microscopic contrast mechanisms sensitive to a scalar projection of the lattice curvature at spatial resolutions down to 100 nm.…”

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Correlating dynamic strain and photoluminescence of solid-state defects with stroboscopic x-ray diffraction microscopy

et al. 2019

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Control of local lattice perturbations near optically-active defects in semiconductors is a key step to harnessing the potential of solid-state qubits for quantum information science and nanoscale sensing. We report the development of a stroboscopic scanning X-ray diffraction microscopy approach for real-space imaging of dynamic strain used in correlation with microscopic photoluminescence measurements. We demonstrate this technique in 4H-SiC, which hosts long-lifetime room temperature vacancy spin defects. Using nano-focused X-ray photon pulses synchronized to a surface acoustic wave launcher, we achieve an effective time resolution of ~100 ps at a 25 nm spatial resolution to map micro-radian dynamic lattice curvatures. The acoustically induced lattice distortions near an engineered scattering structure are correlated with enhanced photoluminescence responses of optically-active SiC quantum defects driven by local piezoelectric effects. These results demonstrate a unique route for directly imaging local strain in nanomechanical structures and quantifying dynamic structure-function relationships in materials under realistic operating conditions.

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Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

Cited by 12 publications

References 38 publications

Spatiotemporal Coherent Control of Thermal Excitations in Solids

Spatiotemporal Coherent Control of Thermal Excitations in Solids

Full Spatiotemporal Control of Laser-Excited Periodic Surface Deformations

Correlating dynamic strain and photoluminescence of solid-state defects with stroboscopic x-ray diffraction microscopy

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