Grazing incidence nanogap resonance in the prism-gap-ferromagnet magneto-plasmonic Otto configuration.

In this Letter, we calculate the optical and magneto-optical reflectivity in a dielectric/gap/ferromagnet excited by a -polarized monochromatic optical beam through the prism (Otto configuration) as a function of the angle of incidence and the gap thickness . Besides the well-known surface plasmon polariton (SPP resonance at  ∼ ), we find a new, to the best of our knowledge, resonance with a nanometric gap  ∼ 10 nm at a large  ∼ 80°. Both resonances display pronounced resonant behavior in the transverse magneto-optical Kerr effect (T-MOKE).

Quantitative Ultrafast Magnetoacoustics at Magnetic Metasurfaces.

Femtosecond (fs) time-resolved magneto-optics is applied to investigate laser-excited ultrafast dynamics of one-dimensional nickel gratings on fused silica and silicon substrates for a wide range of periodicities Λ = 400-1500 nm. Multiple surface acoustic modes with frequencies up to a few tens of GHz are generated. Nanoscale acoustic wavelengths Λ/ have been identified as -spatial harmonics of Rayleigh surface acoustic wave (SAW) and surface skimming longitudinal wave (SSLW), with acoustic frequencies and lifetimes being in agreement with theoretical calculations.

Laser Ultrasound Investigations of AlScN(0001) and AlScN(11-20) Thin Films Prepared by Magnetron Sputter Epitaxy on Sapphire Substrates.

The laser ultrasound (LU) technique has been used to determine dispersion curves for surface acoustic waves (SAW) propagating in AlScN/AlO systems. Polar and non-polar AlScN thin films were prepared by magnetron sputter epitaxy on AlO substrates and coated with a metal layer. SAW dispersion curves have been measured for various propagation directions on the surface.

Nondestructive Femtosecond Laser Lithography of Ni Nanocavities by Controlled Thermo-Mechanical Spallation at the Nanoscale.

We present a new approach to femtosecond direct laser writing lithography to pattern nanocavities in ferromagnetic thin films. To demonstrate the concept, we irradiated 300 nm thin nickel films by single intense femtosecond laser pulses through glass substrate. Using a fluence above the ablation threshold, the process is destructive, leading to the formation of an ablation crater.

Generation of negative group velocity Lamb waves by a moving laser source.

Analytical existence conditions for negative group velocity (NGV) of an arbitrary mode Lamb waves in elastic plate was obtained. Experimentally, NGV waves were excited by means of a thermoelastic laser source moving across the sample plate with a controllable velocity. Such source is coupled with modes which phase velocity component parallel to the surface coincides with the source speed.

Selective generation of Lamb modes by a moving continuous-wave laser.

This Letter focuses on the selectively non-contact generation of Lamb wave modes in plates by using a continuous-wave (CW) laser moving along sample surface. Compared with the generated Lamb waves with broadband, multiple modes (the existence of at least two modes at any given frequency) excited by a pulsed laser, the desired single narrowband mode of the Lamb wave can be generated by a moving CW laser, as long as the scanning speed matches the phase velocity of the mode. Moreover, the dispersion curves of the Lamb wave can be obtained directly from the power spectrum of the time-domain signal recorded at each laser's moving speed.

Self-action of propagating and standing Lamb waves in the plates exhibiting hysteretic nonlinearity: Nonlinear zero-group velocity modes.

An analytical theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous plate material on the Lamb waves near the S zero group velocity point is developed. The theory predicts that the main effect of the hysteretic quadratic nonlinearity consists in the modification of the frequency and the induced absorption of the Lamb modes. The effects of the nonlinear self-action in the propagating and standing Lamb waves are expected to be, respectively, nearly twice and three times stronger than those in the plane propagating acoustic waves.

On the existence of guided acoustic waves at rectangular anisotropic edges.

The existence of acoustic waves with displacements localized at the tip of an isotropic elastic wedge was rigorously proven by Kamotskii, Zavorokhin and Nazarov. This proof, which is based on a variational approach, is extended to rectangular anisotropic wedges. For two high-symmetry configurations of rectangular edges in elastic media with tetragonal symmetry, a criterion is derived that allows identifying the boundary between the regions of existence for wedge modes of even and odd symmetry in regions of parameter space, where even- and odd-symmetry modes do not exist simultaneously.

Transient Grating Spectroscopy in Magnetic Thin Films: Simultaneous Detection of Elastic and Magnetic Dynamics.

Surface magnetoelastic waves are coupled elastic and magnetic excitations that propagate along the surface of a magnetic material. Ultrafast optical techniques allow for a non-contact excitation and detection scheme while providing the ability to measure both elastic and magnetic components individually. Here we describe a simple setup suitable for excitation and time resolved measurements of high frequency magnetoelastic waves, which is based on the transient grating technique.

Laser-generated ultrasonic pulse shapes at solid wedges.

Laser pulses focused near the tip of an elastic wedge generate acoustic waves guided at its apex. The shapes of the acoustic wedge wave pulses depend on the energy and the profile of the exciting laser pulse and on the anisotropy of the elastic medium the wedge is made of. Expressions for the acoustic pulse shapes have been derived in terms of the modal displacement fields of wedge waves for laser excitation in the thermo-elastic regime and for excitation via a pressure pulse exerted on the surface.

Orbital-type trapping of elastic Lamb waves.

The interaction of laser-generated Lamb waves propagating in a plate with a sharp-angle conical hole was studied experimentally and numerically. Part of the energy of the incident wave is trapped within the conic area in two ways: the antisymmetric Lamb wave orbiting the center of the hole and the wave localized at the acute edge. Parameters and conditions for optimal conversion of the incident wave into the trapped modes were studied in this work.

Propagation of flexural waves in inhomogeneous plates exhibiting hysteretic nonlinearity: Nonlinear acoustic black holes.

Theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous material on flexural wave in the plates of continuously varying thickness is developed. For the wedges with thickness increasing as a power law of distance from its edge strong modifications of the wave dynamics with propagation distance are predicted. It is found that nonlinear absorption progressively disappearing with diminishing wave amplitude leads to complete attenuation of acoustic waves in most of the wedges exhibiting black hole phenomenon.

Accurate characterization of SiO2 thin films using surface acoustic waves.

We have investigated the acoustic properties of silicon dioxide thin films. Therefore, we determined the phase velocity dispersion of LiNbO3 substrate covered with SiO2 deposited by a plasma enhanced chemical vapor deposition and a physical vapor deposition (PVD) process using differential delay lines and laser ultrasonic method. The density p and the elastic constants (c11 and c44) can be extracted by fitting corresponding finite element simulations to the phase velocities within an accuracy of at least +4%.

[Inheritable changes in miRNAs expression in HeLa cells after X-ray and mitomycin C treatment].

We identified 40 miRNAs with inherited aberrant expression by multiple parallel sequencing of human HeLa cells irradiated with X rays and mitomycin C. Twenty-two miRNAs were repressed and 15 miRNAs were induced after radiation and mytomycin C treatment. The expression of three miRNAs (miR-10b-5p, miR-148a-3p, and miR-340-5p) decreased after X-ray exposure and increased after mitomycin C treatment.

[Coordinated aberranit expression of miRNAs in colon cancer].

Applying the method of multiple parallel sequencing on the MiSeq platform (Illumina, United States), a comparative analysis of miRNA expression in tumor and normal colon tissuie cells was performed. Forty miRNAs aberrantly expressed in cancer were detected. Among them, 15 and 25 miRNAs showed increased arid decreased expression, respectively, for all or most of the cases.

Laser-based linear and nonlinear guided elastic waves at surfaces (2D) and wedges (1D).

The characteristic features and applications of linear and nonlinear guided elastic waves propagating along surfaces (2D) and wedges (1D) are discussed. Laser-based excitation, detection, or contact-free analysis of these guided waves with pump-probe methods are reviewed. Determination of material parameters by broadband surface acoustic waves (SAWs) and other applications in nondestructive evaluation (NDE) are considered.

Evaluation of third-order elastic constants using laser-generated multi-type ultrasound for isotropic materials.

Within the linear elasticity approximation the speed of a small-amplitude sound in conventional linear elasticity is determined only by the second order elastic (SOE) constants and the density of the medium. Subjecting the conveying solid to a static strain of a sufficient magnitude introduces the third-order elastic (TOE) constants in the equation of the sound speed. In this work we applied a homogeneous isotropic deformation caused by a thermal expansion of an aluminum alloy sample.

Fragmentation of DNA in a sub-microliter microfluidic sonication device.

Fragmentation of DNA is an essential step for many biological applications including the preparation of next-generation sequencing (NGS) libraries. As sequencing technologies push the limits towards single cell and single molecule resolution, it is of great interest to reduce the scale of this upstream fragmentation step. Here we describe a miniaturized DNA shearing device capable of processing sub-microliter samples based on acoustic shearing within a microfluidic chip.

Nanoscale noncontact subsurface investigations of mechanical and optical properties of nanoporous low-k material thin film.

Revealing defects and inhomogeneities of physical and chemical properties beneath a surface or an interface with in-depth nanometric resolution plays a pivotal role for a high degree of reliability in nanomanufacturing processes and in materials science more generally. (1, 2) Nanoscale noncontact depth profiling of mechanical and optical properties of transparent sub-micrometric low-k material film exhibiting inhomogeneities is here achieved by picosecond acoustics interferometry. On the basis of the optical detection through the time-resolved Brillouin scattering of the propagation of a picosecond acoustic pulse, depth profiles of acoustical velocity and optical refractive index are measured simultaneously with spatial resolution of tens of nanometers.

Solitary surface acoustic waves and bulk solitons in nanosecond and picosecond laser ultrasonics.

Recent achievements of nonlinear acoustics concerning the realization of solitons and solitary waves in crystals and their surfaces attained by nanosecond and picosecond laser ultrasonics are discussed and compared. The corresponding pump-probe setups are described, which allow an all-optical contact-free excitation and detection of short strain pulses in the broad frequency range between 10 MHz and about 300 GHz. The formation of solitons in the propagating longitudinal strain pulses is investigated for nonlinear media with intrinsic lattice-based dispersion.

Nonlinear surface acoustic waves: realization of solitary pulses and fracture.

A laser-based technique for the contact-free generation and detection of strongly nonlinear surface acoustic wave (SAW) pulses with amplitudes limited by the materials strength has been developed. The effects of nonlinear propagation of short elastic surface pulses with finite strength in isotropic solids, such as fused quartz, anisotropic solids, such as silicon, and dispersive media were investigated. Solitary surface wave propagation was observed in layered structures for normal and anomalous dispersion.

Intrinsic strength of silicon crystals in pure- and combined-mode fracture without precrack.

Measurement of the critical fracture strength of single-crystal silicon was carried out by contact-free laser-based excitation and detection of nonlinear surface acoustic wave (SAW) pulses. The three crystallographic geometries Si(112)111[over ], Si(112)1[over ]1[over ]1, and Si(110)11[over ]1 were examined. A comparison of the optically detected SAW transients and numerically calculated stress-strain fields allowed an estimate of the intrinsic mechanical strength without using an artificial precrack.

Solitary surface acoustic waves.

Solitary acoustic pulses can propagate along the surface of a coated homogeneous and inhomogeneous medium. It is shown how these nonlinear surface acoustic waves evolve out of initial pulselike conditions generated by pulsed laser excitation and how they can be monitored by optical detection. The solitary pulse shapes at the surface are computed on the basis of an evolution equation with nonlocal nonlinearity.

[Mixed monolayers of amphiphile-modified nucleic bases and diynoic acids. I. Phase states at air-water interface and in Langmuir-Blodgett films].

Monolayers of amphiphile-modified nucleic bases with diynoic acid were obtained and characterized. The synthesized nucleic bases contained in the monolayer complementarily bind the nucleotide molecules contained in the aqueous subphase, and the structure of the resulting monolayers can be fixed by the photopolymerization of diynoic acid. The resulting monolayer exemplifies a novel type of model systems for investigating molecular recognition at the surface of biological membranes.