Ultrafast laser pulse chirp effects on laser-generated nanoacoustic strains in Silicon

Bakarezos, Makis; Tzianaki, E.; Petrakis, Stelios; Tsibidis, George D.; Loukakos, P. A.; Dimitriou, Vanda; Kosmidis, C.; Tatarakis, M.; Papadogiannis, N. A.

doi:10.1016/j.ultras.2018.01.008

Cited by 8 publications

(4 citation statements)

References 44 publications

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“…Nevertheless, the dynamic response of the modified structures must be experimentally studied and confirmed. Laser interferometric methods used to study vibrations in such small scales [63–66] could be applied to the modified metamaterial structures to verify the simulation results of the dynamic response. The present study illustrates the significance of fabricating mechanical metamaterials by preserving the microscale resolution.…”

Section: Discussionmentioning

confidence: 99%

Vacancies for controlling the behavior of microstructured three-dimensional mechanical metamaterials

Vangelatos

Komvopoulos

Grigoropoulos

2018

Mathematics and Mechanics of Solids

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Mechanical metamaterials are designed to exhibit enhanced properties not found in natural materials or to bolster the properties of existing materials. The theoretical foundations for tuning the mechanical properties have been established, including topological states, controllable buckling behavior, and quasi-two-dimensional mechanical metamaterials with structures containing vacancies. However, the fabrication and experimental procedures to study these structures at the microscale have not been developed yet and the three-dimensional (3D) architectures examined to date are fairly limited. In this study, 3D mechanical metamaterial structures with select unit cells designed to have vacancies were fabricated by multi-photon lithography, having as the principal objective to control (localize) failure and increase the strain energy capacity of the structure. The metamaterial structure from which all the current designs originate is the octet-truss structure, one of the most widely studied 3D metamaterials. The design of the structures was inspired by the role of vacancies in crystal lattices. Vacancies were introduced in the metamaterial structures to allow localized buckling of lattice members to occur in specific unit cells. The significant increase of the strain energy dissipated in these metamaterials is demonstrated by nanoindentation experiments and finite element results. Vacancy effects on the dynamic response of metamaterial structures are also examined in the light of modal analysis simulations. The findings of this study illustrate the importance of strategically placing vacancies in the microlattices of metamaterial structures to control the overall mechanical behavior and greatly increase strain energy dissipation.

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Section: Discussionmentioning

confidence: 99%

Vacancies for controlling the behavior of microstructured three-dimensional mechanical metamaterials

Vangelatos

Komvopoulos

Grigoropoulos

2018

Mathematics and Mechanics of Solids

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“…The lock-in amplifier can detect extremely small signal differences between the reference and reflected beams at the modulating frequency of the pump beam, that is, at a frequency of 270 Hz imposed by a mechanical chopper placed in the pump line. The detected signal differences arise from changes in the reflectivity of the probe beam reflected by the sample and can be of the order of ~ 10 −5 , as inferred from the experimental measurements [6]. Therefore, it is important to ensure that the beams reaching the balanced photodiode are of equal power in the absence of any pump-induced phenomenon, so that the differential signal is zero, disregarding the noise from the lock-in amplifier electronics, which is of the order of 10 -7 .…”

Section: Pump-probe Experimentsmentioning

confidence: 92%

“…Therefore, it is important to ensure that the beams reaching the balanced photodiode are of equal power in the absence of any pump-induced phenomenon, so that the differential signal is zero, disregarding the noise from the lock-in amplifier electronics, which is of the order of 10 -7 . The technique applied here, that is, detection via the balanced photodiode and the lock-in amplifier components, is used to achieve an improved level of Signalto-Noise Ratio (SNR), desired in such measurements, and constitutes a key factor for the successful conduction of this type of research experiments [6].…”

Section: Pump-probe Experimentsmentioning

confidence: 99%

“…Nanostructured materials and layers of sub-micrometer thickness can be probed and characterized with nanometer resolution, through generated acoustic phonons with frequencies that can extend up to the GHz range [3]. Such an approach has been successfully adopted for the characterization of materials of high technological importance, arising from their special structural and thermo-elastic characteristics [5][6][7], while a remarkably broad spectrum of applications has been demonstrated, expanding from the investigation of the structural integrity of materials in engineering [8] and the characterization of biological samples [9], to the Inertial Fusion Energy studies IFE ( [10] and references therein). For instance, in IFE, the early time symmetry tuning of the ablator and of the quality of laser irradiation is crucial.…”

Section: Introductionmentioning

confidence: 99%

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Pump-probe reflectivity studies of ultrashort laser-induced acousto-mechanical strains in ZnO films

Kosma,

Kaleris,

Kaselouris

et al. 2023

Appl. Phys. A

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In the current work we report on the generation of acoustic strains in thin ZnO layers using optoacoustic transduction of ultrashort laser pulses into acoustic waves on an Au thin film transducer. After absorption of energy by the electron system of the metal, energy conversion, thermal expansion and mechanical deformation takes place. The generation and propagation of the induced acoustic strains are monitored in time via a degenerate pump-probe transient reflectivity optical setup at 800 nm, as opposed to most commonly used schemes that employ different wavelengths for the pump and probe beams, mostly in the vicinity of ZnO maximum absorption. The experimental results include energy relaxation times and phonon scattering frequencies and are supported by a thermal vibro-acoustic finite element model. The model is based on the combination of a revised two-temperature approach and elasticity theory, and considers anisotropic properties for the ZnO film and the computation of the elastic wave velocity for the first time. The outcomes are discussed in the context of electron–phonon coupling factors and other material properties. A good agreement between the experimental findings and the results from the numerical simulations has been established, regarding outcomes like the mean velocity of the strain waves, establishing a novel characterization method applicable to a variety of materials and structures.

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Novel Light Sources Beyond FELs

Korol,

Solov’yov

2022

Lecture Notes in Nanoscale Science and Technology

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Ultrafast laser pulse chirp effects on laser-generated nanoacoustic strains in Silicon

Cited by 8 publications

References 44 publications

Vacancies for controlling the behavior of microstructured three-dimensional mechanical metamaterials

Vacancies for controlling the behavior of microstructured three-dimensional mechanical metamaterials

Pump-probe reflectivity studies of ultrashort laser-induced acousto-mechanical strains in ZnO films

Novel Light Sources Beyond FELs

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