Search results for "EMT"
showing 10 items of 413 documents
Hot-Carrier Generation in Plasmonic Nanoparticles: The Importance of Atomic Structure
2020
Metal nanoparticles are attractive for plasmon-enhanced generation of hot carriers, which may be harnessed in photochemical reactions. In this work, we analyze the coherent femtosecond dynamics of photon absorption, plasmon formation, and subsequent hot-carrier generation through plasmon dephasing using first-principles simulations. We predict the energetic and spatial hot-carrier distributions in small metal nanoparticles and show that the distribution of hot electrons is very sensitive to the local structure. Our results show that surface sites exhibit enhanced hot-electron generation in comparison to the bulk of the nanoparticle. While the details of the distribution depend on particle s…
Imbibition of Femtoliter-Scale DNA-Rich Aqueous Droplets into Porous Nylon Substrates by Molecular Printing
2019
This work presents the first reported imbibition mechanism of femtoliter (fL)-scale droplets produced by microchannel cantilever spotting (μCS) of DNA molecular inks into porous substrates (hydrophilic nylon). Differently from macroscopic or picoliter droplets, the downscaling to the fL-size leads to an imbibition process controlled by the subtle interplay of evaporation, spreading, viscosity, and capillarity, with gravitational forces being quasi-negligible. In particular, the minimization of droplet evaporation, surface tension, and viscosity allows for a reproducible droplet imbibition process. The dwell time on the nylon surface permits further tuning of the droplet lateral size, in acc…
Femtosecond laser pulse shaping for enhanced ionization
2009
El pdf del artículo es la versión post-print: arXiv:0906.1938v1
Charge and spin photocurrents in the Rashba model
2017
In metallic noncentrosymmetric crystals and at surfaces the response of spin currents and charge currents to applied electric fields contains contributions that are second order in the electric field, which are forbidden by symmetry in centrosymmetric systems. Thereby, photocurrents and spin photocurrents can be generated in inversion asymmetric metals by the application of femtosecond laser pulses. We study the laser-induced charge current in the ferromagnetic Rashba model with in-plane magnetization and find that this \textit{magnetic photogalvanic effect} can be tuned to be comparable in size to the laser-induced photocurrents measured experimentally in magnetic bilayer systems such as C…
Oil-in-Water fL Droplets by Interfacial Spontaneous Fragmentation and Their Electrical Characterization
2019
Inkjet printing is here employed for the first time as a method to produce femtoliter-scale oil droplets dispersed in water. In particular, picoliter-scale fluorinated oil (FC40) droplets are printed in the presence of perfluoro-1-octanol surfactant at a velocity higher than 5 m/s. Femtoliter-scale oil droplets in water are spontaneously formed through a fragmentation process at the water/air interface using minute amounts of nonionic surfactant (down to 0.003% v/v of Tween 80). This fragmentation occurs by a Plateau-Rayleigh mechanism at a moderately high Weber number (10(1)). A microfluidic chip with integrated microelectrodes allows droplets characterization in terms of number and diamet…
Optical Diagnostics with Ultrafast and Strong Field Raman Techniques
2014
In this chapter, we will discuss some coherent techniques, namely Raman Induced Polarization Spectroscopy (RIPS) and femtosecond Coherent Raman Anti-Stokes Spectroscopy (fs-CARS). We will demonstrate their ability to be used as non-invasive optical diagnostic tools for temperature, density, or concentration measurements, as well as a means of testing collision induced energy transfer models (in a low field regime), and studying the so-called inhomogeneous lineshape effects that are particularly enhanced in the case of hydrogen. We will also show how molecular alignment achieved in a strong field regime can provide additional information about collisional relaxation processes. In all cases, …
Three-Dimensional Printing of Nonlinear Optical Lenses.
2018
In the current paper, a series of nonlinear optical (NLO) active devices was prepared by utilizing stereolithographic three-dimensional printing technique. Microcrystalline NLO active component, urea, or potassium dihydrogen phosphate was dispersed in a simple photopolymerizable polyacrylate-based resin and used as the printing material to fabricate highly efficient transparent NLO lenses. The nonlinear activity of the printed lenses was confirmed by second-harmonic generation measurements using a femtosecond laser-pumped optical parametric amplifier operating at a wavelength of 1195 nm. The three-dimensional printing provides a simple method to utilize a range of NLO active compounds witho…
Femtosecond four-wave-mixing spectroscopy of suspended individual semiconducting single-walled carbon nanotubes.
2010
Femtosecond four-wave-mixing (FWM) experiments of individual suspended semiconducting single-walled carbon nanotubes (SWCNTs) are presented. The chiral indices of the tubes were determined by electron diffraction as (28,14) and (24,14) having diameters of 2.90 and 2.61 nm, respectively. The diameter and semiconducting character of the tubes were additionally confirmed by resonance Raman measurements. The FWM signal showed electronic response from the SWCNTs. The results demonstrate that ultrafast dynamics of individual SWCNTs can be studied by FWM spectroscopies.
Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation
2015
Abstract A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp 3 bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp 3 percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not…
Filamentation-induced spectral broadening and pulse shortening of infrared pulses in Tellurite glass
2016
Abstract Filamentation of infrared femtosecond pulses in Tellurite glass is reported, leading to the generation of a supercontinuum generation spanning from the visible up to 4 μm. The angular distribution of the supercontinuum shows clear evidence of conical waves generation, in particular, in the visible region. Moreover, taking advantage of the spatio-temporal self-focusing effect occurring in the Tellurite glass, a twofold pulse shortening is demonstrated. Tellurite glass appears as a very convenient, versatile and promising medium for femtosecond nonlinear optics in the infrared region.