We have studied processes of interaction of pulsed laser radiation with resonant groups of plasmonic nanoparticles（resonant domains） in large colloidal nanoparticle aggregates having different ...interparticle gaps and particle size distributions.These processes are responsible for the origin of nonlinear optical effects and photochromic reactions in multiparticle aggregates.To describe photo-induced transformations in resonant domains and alterations in their absorption spectra remaining after the pulse action,we introduce the factor of spectral photomodification.Based on calculation of changes in thermodynamic,mechanical,and optical characteristics of the domains,the histograms of the spectrum photomodification factor have been obtained for various interparticle gaps,an average particle size,and the degree of polydispersity.Variations in spectra have been analyzed depending on the intensity of laser radiation and various combinations of size characteristics of domains.The obtained results can be used to predict manifestation of photochromic effects in composite materials containing different plasmonic nanoparticle aggregates in pulsed laser fields.
Interactions of pulsed laser radiation with resonance domains of multiparticle colloidal aggregates having an increasingly complex local environment are studied via an optodynamic model. The model is ...applied to the simplest configurations, such as single particles, dimers, and trimers consisting of mono- and polydisperse Ag nanoparticles. We analyze how the local environment and the associated local field enhancement by surrounding particles affect the optodynamic processes in domains, including their photomodification and optical properties.
When an erbium-laser pulse is directed into water through a small-diameter fiber tip (FT), the absorption of the laser energy superheats the water and its boiling induces a vapor bubble. We present ...the influence of different FT geometries and pulse parameters on the vapor-bubble dynamics. In our investigation, we use a free-running erbium: yttrium aluminum garnet (Er:YAG) (
) laser that was designed for laser dentistry. Its pulse is directed into the water through FTs with a flat and conical geometry. Our results show that in the case of the conical FT, a spherical bubble is induced, while a channel-like bubble develops for the flat FT. The ratio between the mechanical energy of the liquid medium and the pulse energy, which we call the optodynamic energy-conversion efficiency, is examined using shadow photography. The results indicate that this efficiency is significantly larger when a conical FT is used and it increases with increasing pulse energy and decreasing pulse duration. The spherical bubbles are compared with the Rayleigh model in order to present the influence of the pulse duration on the dynamics of the bubble's expansion.
Erbium:yttrium aluminum garnet laser cleaning is a promising technique in endodontic treatment. In our in vitro study, we measured the vapor-bubble dynamics in the root canal by using shadow ...photography. The canal model was made of a plastic cutout placed between two transparent glass plates. An artificial smear layer was applied to the glass to study cleaning efficiency. In our results, no shock waves have been observed, since the pulp-chamber dimensions have been in the same range as the maximum diameter of the vapor bubble. This leads to the conclusion that shock waves are not the main cleaning mechanism within our model. However, the cleaning effects are also visible in the regions significantly below the bubble. Therefore, it can be concluded that fluid flow induced by the bubble's oscillations contributes significantly to the canal cleaning. We also proposed a simple theoretical model for cleaning efficiency and used it to evaluate the measured data.
•Modeling using Green’s function formalism and streamlined Huygens’ principle.•The model incorporates spatial distributions of source and sensor sensitivity.•A statistically simplified area-to-area ...ultrasound transfer function was developed.•Uniform, Gaussian and annular source ultrasonic waveforms are simulated.•Thus-simulated waveforms match the measurements more closely than the point model.
The near-field, surface-displacement waveforms in plates are modeled using interwoven concepts of Green’s function formalism and streamlined Huygens’ principle. Green’s functions resemble the building blocks of the sought displacement waveform, superimposed and weighted according to the simplified distribution. The approach incorporates an arbitrary circular spatial source distribution and an arbitrary circular spatial sensitivity in the area probed by the sensor. The displacement histories for uniform, Gaussian and annular normal-force source distributions and the uniform spatial sensor sensitivity are calculated, and the corresponding weight distributions are compared. To demonstrate the applicability of the developed scheme, measurements of laser ultrasound induced solely by the radiation pressure are compared with the calculated waveforms. The ultrasound is induced by laser pulse reflection from the mirror-surface of a glass plate. The measurements show excellent agreement not only with respect to various wave-arrivals but also in the shape of each arrival. Their shape depends on the beam profile of the excitation laser pulse and its corresponding spatial normal-force distribution.
Optodynamic interaction between a laser pulse and the surface of an opaque, solid elastic object produces transient waves that propagate and reverberate within the object. They can be, in general, ...categorized into three distinctive types which are all formed through different mechanisms: ablation-induced waves, light-pressure-induced waves, and thermoelastic waves. In this paper, out-of-plane displacements of such waves are simulated at the epicentral position on the opposite side of an extended plane-parallel elastic plate. Wave propagation is mathematically described by Green’s transfer functions convolved with suitable time profiles of the incoming laser pulses. The simulated size of the circularly symmetric laser-illuminated area on the plate surface is varied to show the limit-to-limit transition of the displacement waveforms: from a 2D point source to an infinite 1D source.
We use an optodynamic model to study the interaction of pulsed laser radiation of different duration with mono- and polydisperse dimers and trimers of plasmonic nanoparticles as resonant domains of ...colloid Ag multiparticle aggregates. A comparative analysis of the influence of pulse duration on the kinetic characteristics of domains accompanied by the change in their local structure was carried out taking into account the intensity of incident radiation. The obtained results explain the reasons for laser photochromic reactions in materials containing colloidal aggregates of plasmonic nanoparticles.
High-intensity light from a laser pulse can produce laser-induced breakdown in a liquid followed by a shock wave and the growth of a cavitation bubble. When the bubble reaches its maximum radius, the ...pressure of the surrounding liquid causes it to collapse; this results in bubble oscillations. The cavitation bubble's oscillations and the corresponding shock waves were measured from the deflections of a laser beam. These deflections were detected using a fast quadrant photodiode, built into the optical probe. The precise relative-positioning system and the small diameter of the beam's waist made it possible to detect and analyse the signals from the shock wave and the cavitation bubble. Here, we have demonstrated that a method based on a beam-deflection probe can be used to measure the fast phenomena that follow immediately after laser-induced breakdown as well as the whole dynamics of the bubble oscillations, which corresponds to a three-orders-of-magnitude larger time scale.
Interactions of pulsed laser radiation with resonance domains of multiparticle colloidal aggregates having an increasingly complex local environment are studied via an optodynamic model. The model is ...applied to the simplest configurations, such as single particles, dimers, and trimers consisting of mono- and polydisperse Ag nanoparticles. We analyze how the local environment and the associated local feld enhancement by surrounding particles affect the optodynamic processes in domains, including their photomodification and optical properties.
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