Showing papers on "Femtosecond published in 2015"
TL;DR: This work demonstrates an all-optical technique to reconstruct momentum-dependent band gaps by exploiting the coherent motion of electron-hole pairs driven by intense midinfrared femtosecond laser pulses, and identifies the split-off valence band as making the greatest contribution to tunneling to the conduction band.
Abstract: The band structure of matter determines its properties. In solids, it is typically mapped with angle-resolved photoemission spectroscopy, in which the momentum and the energy of incoherent electrons are independently measured. Sometimes, however, photoelectrons are difficult or impossible to detect. Here we demonstrate an all-optical technique to reconstruct momentum-dependent band gaps by exploiting the coherent motion of electron-hole pairs driven by intense midinfrared femtosecond laser pulses. Applying the method to experimental data for a semiconductor ZnO crystal, we identify the split-off valence band as making the greatest contribution to tunneling to the conduction band. Our new band structure measurement technique is intrinsically bulk sensitive, does not require a vacuum, and has high temporal resolution, making it suitable to study reactions at ambient conditions, matter under extreme pressures, and ultrafast transient modifications to band structures.
399 citations
TL;DR: It is shown that undesirable free-carrier effects can be suppressed by a proper spectral positioning of the magnetic resonance, making such a structure the fastest all-optical switch operating at the nanoscale.
Abstract: We demonstrate experimentally ultrafast all-optical switching in subwavelength nonlinear dielectric nanostructures exhibiting localized magnetic Mie resonances. We employ amorphous silicon nanodisks to achieve strong self-modulation of femtosecond pulses with a depth of 60% at picojoule-per-disk pump energies. In the pump–probe measurements, we reveal that switching in the nanodisks can be governed by pulse-limited 65 fs-long two-photon absorption being enhanced by a factor of 80 with respect to the unstructured silicon film. We also show that undesirable free-carrier effects can be suppressed by a proper spectral positioning of the magnetic resonance, making such a structure the fastest all-optical switch operating at the nanoscale.
389 citations
TL;DR: In this paper, a hierarchical nano/microstructure with femtosecond laser pulses was created for light collection and water/dust repelling, and the effect of superhydrophobicity and self-cleaning was demonstrated by a falling water droplet repelled away from a structured surface with 30% of the droplet kinetic energy conserved.
Abstract: In this study, we create a multifunctional metal surface by producing a hierarchical nano/microstructure with femtosecond laser pulses. The multifunctional surface exhibits combined effects of dramatically enhanced broadband absorption, superhydrophobicity, and self-cleaning. The superhydrophobic effect is demonstrated by a falling water droplet repelled away from a structured surface with 30% of the droplet kinetic energy conserved, while the self-cleaning effect is shown by each water droplet taking away a significant amount of dust particles on the altered surface. The multifunctional surface is useful for light collection and water/dust repelling.
363 citations
TL;DR: The advent of hard X-ray free-electron lasers has opened a new chapter in macromolecular crystallography and the prospects of serial femtosecond crystallography are described.
263 citations
TL;DR: By mapping nuclear motions using femtosecond x-ray pulses, this work has created real-space representations of the evolving dynamics during a well-known chemical reaction and shown a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-rays.
Abstract: Structural rearrangements within single molecules occur on ultrafast time scales. Many aspects of molecular dynamics, such as the energy flow through excited states, have been studied using spectroscopic techniques, yet the goal to watch molecules evolve their geometrical structure in real time remains challenging. By mapping nuclear motions using femtosecond x-ray pulses, we have created real-space representations of the evolving dynamics during a well-known chemical reaction and show a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-ray scattering. A computational analysis optimally matches the series of scattering patterns produced by the x rays to a multitude of potential reaction paths. In so doing, we have made a critical step toward the goal of viewing chemical reactions on femtosecond time scales, opening a new direction in studies of ultrafast chemical reactions in the gas phase.
254 citations
TL;DR: The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat and the spectral response is examined and finds a constant spectral responsivity of between 500 and 1,500 nm, consistent with efficient electron heating.
Abstract: Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies have addressed the general operation of graphene-based photothermoelectric devices and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster timescale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 fs. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 fs laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity of between 500 and 1,500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.
249 citations
TL;DR: In this article, a resonant high-order harmonic generation of an elliptical laser pulse was proposed to measure photoelectron circular dichroism on chiral molecules, opening the route to table-top time-resolved femtosecond and attosecond chiroptical experiments.
Abstract: Circular dichroism in the extreme ultraviolet range is broadly used as a sensitive structural probe of matter, from the molecular photoionization of chiral species1, 2, 3 to the magnetic properties of solids4. Extending such techniques to the dynamical regime has been a long-standing quest of solid-state physics and physical chemistry, and was only achieved very recently5 thanks to the development of femtosecond circular extreme ultraviolet sources. Only a few large facilities, such as femtosliced synchrotrons6, 7 or free-electron lasers8, are currently able to produce such pulses. Here, we propose a new compact and accessible alternative solution: resonant high-order harmonic generation of an elliptical laser pulse. We show that this process, based on a simple optical set-up, delivers bright, coherent, ultrashort, quasi-circular pulses in the extreme ultraviolet. We use this source to measure photoelectron circular dichroism on chiral molecules, opening the route to table-top time-resolved femtosecond and attosecond chiroptical experiments.
221 citations
TL;DR: In this article, the authors present a physical scenario that couples electrodynamics, describing surface plasmon excitation, with hydrographic dynamics, describing Marangoni convection and counter-rolls, to elucidate this important subablation regime of light-matter interaction in which matter is being modified.
Abstract: Materials irradiated with multiple femtosecond laser pulses in subablation conditions are observed to develop various types of self-assembled morphologies that range from nanoripples to periodic microgrooves and quasiperiodic microspikes. Here, we present a physical scenario that couples electrodynamics, describing surface plasmon excitation, with hydrodynamics, describing Marangoni convection and counter-rolls, to elucidate this important subablation regime of light-matter interaction in which matter is being modified; however, the underlying process is not yet fully understood. The proposed physical mechanism could be generally applicable to practically any conductive material structured by ultrashort laser pulses; therefore it can be useful for the interpretation of further critical aspects of light-matter interaction.
204 citations
TL;DR: In this article, a novel method is proposed to enable the control on the self-amplitude modulation (SAM) of TI by adjusting its dopant type, which results in more capacity for excited carriers than the n-type TI.
Abstract: Mechanically triturated n- and p-type Bi2Te3 nanoparticles, the nanoscale topological insulators (TIs), are employed as nonlinear saturable absorbers to passively mode-lock the erbium-doped fiber lasers (EDFLs) for sub-400 fs pulse generations. A novel method is proposed to enable the control on the self-amplitude modulation (SAM) of TI by adjusting its dopant type. The dopant type of TI only shifts the Fermi level without changing its energy bandgap, that the n- and p-type Bi2Te3 nanoparticles have shown the broadband saturable absorption at 800 and 1570 nm. In addition, both the complicated pulse shortening procedure and the competition between hybrid mode-locking mechanisms in the Bi2Te3 nanoparticle mode-locked EDFL system have been elucidated. The p-type Bi2Te3 with its lower effective Fermi level results in more capacity for excited carriers than the n-type Bi2Te3, which shortens the pulse width by enlarging the SAM depth. However, the strong self-phase modulation occurs with reduced linear loss and...
198 citations
TL;DR: The analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses.
Abstract: Few-femtosecond synchronization at free-electron lasers is key for nearly all experimental applications, stable operation and future light source development. Here, Schulz et al. demonstrate all-optical synchronization of the soft X-ray FEL FLASH to better than 30 fs and illustrate a pathway to sub-10 fs.
197 citations
TL;DR: In this paper, a high-Q lithium niobate (LN) whispering gallery mode (WGM) microresonators suspended on silica pedestals were fabricated by femtosecond laser direct writing followed by focused ion beam (FIB) milling.
Abstract: We report on fabrication of high-Q lithium niobate (LN) whispering-gallery-mode (WGM) microresonators suspended on silica pedestals by femtosecond laser direct writing followed by focused ion beam (FIB) milling. The micrometer-scale (diameter ~82 μm) LN resonator possesses a Q factor of ~2.5 × 105 around 1550 nm wavelength. The combination of femtosecond laser direct writing with FIB enables high-efficiency, high-precision nanofabrication of high-Q crystalline microresonators.
TL;DR: A description of the X-ray Pump–Probe (XPP) instrument at the Linac Coherent Light Source is presented and recent scientific highlights illustrate the versatility and the time-resolved X-rays diffraction and spectroscopy capabilities of the instrument.
Abstract: The X-ray Pump–Probe instrument achieves femtosecond time-resolution with hard X-ray methods using a free-electron laser source. It covers a photon energy range of 4–24 keV. A femtosecond optical laser system is available across a broad spectrum of wavelengths for generating transient states of matter. The instrument is designed to emphasize versatility and the scientific goals encompass ultrafast physical, chemical and biological processes involved in the transformation of matter and transfer of energy at the atomic scale.
TL;DR: Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma, which could presage a more generally efficient means of creating x-ray pulses for fundamental dynamics studies as well as technological applications.
Abstract: High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the emission from each species is highest when a short-wavelength ultraviolet driving laser is used. However, phase matching--the constructive addition of x-ray waves from a large number of atoms--favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth-limited pulse trains of ~100 attoseconds.
TL;DR: The authors' results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale.
Abstract: Light absorption can trigger biologically relevant protein conformational changes The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion Here we report direct experimental evidence of such 'proteinquake' observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion As the system approaches equilibrium it undergoes damped oscillations with a ~36-picosecond time period Our results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale
TL;DR: A novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation based on ultrafast photoinjection of dense electron-hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity.
Abstract: We propose a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photoinjection of dense (>1020 cm–3) electron–hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows manipulation by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20% tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such a single-particle nanodevice enables designing of fast and ultracompact optical switchers and modulators.
TL;DR: In this paper, a femtosecond optical spectroscopy and single-shot electron diffraction measurements during the photoinduced amorphization of the phase-change material Ge2Sb2Te5 demonstrate that optical properties can be separated from the structural state.
Abstract: Femtosecond optical spectroscopy and single-shot electron diffraction measurements during the photoinduced amorphization of the phase-change material Ge2Sb2Te5 demonstrate that optical properties can be separated from the structural state. The extreme electro-optical contrast between crystalline and amorphous states in phase-change materials is routinely exploited in optical data storage1 and future applications include universal memories2, flexible displays3, reconfigurable optical circuits4,5, and logic devices6. Optical contrast is believed to arise owing to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase-change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 fs owing to a rapid depletion of electrons from resonantly bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2-ps time constant. The optical changes are an order of magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes.
TL;DR: In this article, a Runge-Kutta-4 numerical algorithm was used to model the heat diffusion around a spherical gold nanoparticle, and the influence of the nanoparticle diameter, pulse duration, wavelength, and Kapitza resistivity in order to explain the observations reported in the literature.
Abstract: Under nano- to femtosecond pulsed illumination at their plasmonic resonance wavelength, metal nanoparticles efficiently absorb the incident light energy that is subsequently converted into heat. In a liquid environment, with sufficiently high pulse fluences (light energy per unit area), this heat generation may result in the local formation of a transient nanobubble. This phenomenon has been the subject of a decade of investigations and is at the basis of numerous applications from cancer therapy to photoacoustic imaging. The aim of this article is to clarify the question of the fluence threshold required for bubble formation. Using a Runge-Kutta-4 numerical algorithm modeling the heat diffusion around a spherical gold nanoparticle, we numerically investigate the influence of the nanoparticle diameter, pulse duration (from the femto- to the nanosecond range), wavelength, and Kapitza resistivity in order to explain the observations reported in the literature.
TL;DR: These measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances and establish that mediation through electronically excited molecular states is a key mechanistic feature.
Abstract: Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectroscopy with ultrafast X-ray emission spectroscopy and diffuse X-ray scattering at the SACLA facility to track the non-equilibrated electronic and structural dynamics within a bimetallic donor-acceptor complex that contains an optically dark centre. Exploiting the 100-fold increase in temporal resolution as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined.
TL;DR: In this paper, the authors reveal a new paradigm for long-range, low-loss, ultrahigh power ultrashort pulse propagation at mid-infrared wavelengths in the atmosphere.
Abstract: Mid-infrared ultrashort high energy laser sources are opening up new opportunities in science, including keV-class high harmonic generation and monoenergetic MeV-class proton acceleration. As new higher energy sources become available, potential applications for atmospheric propagation can dramatically grow to include stand-off detection, laser communications, shock-driven remote terahertz enhancement and extended long-lived thermal waveguides to transport high power microwave and radiofrequency waves. We reveal a new paradigm for long-range, low-loss, ultrahigh power ultrashort pulse propagation at mid-infrared wavelengths in the atmosphere. Before the onset of critical self-focusing, energy in the fundamental wave continually leaks into shock-driven spectrally broadened higher harmonics. A persistent near-invariant solitonic leading edge on the multi-terawatt pulse waveform transports most of the power over hundred-metre-long distances. Such light bullets are resistant to uncontrolled multiple filamentation and are expected to spark extensive research in optics, where the use of mid-infrared lasers is currently much under-utilized. A mechanism for the propagation of mid-infrared femtosecond laser pulses in air is theoretically investigated. A numerical simulation predicts that the propagation of multiple-terawatt pulses is possible over hundreds of metres.
TL;DR: The results demonstrated that the microfiber-based TI PLD film SA is a promising device for practical multi-GHz ultrashort pulses generation and proposed a newly explanation for the impact of nonlinear effect of SA on the harmonic mode-locking behavior.
Abstract: By utilizing the pulsed laser deposition (PLD) method, we fabricated a kind of microfiber-based topological insulator (TI) saturable absorber (SA) which has inherent merits of effective and robust properties. We also proposed a newly explanation for the impact of nonlinear effect of SA on the harmonic mode-locking (HML) behavior. Upon employing on the SA, we achieved stable fundamental mode-locking (FML) at central wavelength of 1562.4 nm with pulse duration as short as 320 fs. By adjusting the intracavity polarization state at maximum pump power of 395 mW, we obtained stable femtosecond harmonic soliton pulse generation with repetition rate of 2.95 GHz and output power of 45.3 mW. Our results demonstrated that the microfiber-based TI PLD film SA is a promising device for practical multi-GHz ultrashort pulses generation.
TL;DR: This work demonstrates filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time and shows that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament.
Abstract: Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared.
TL;DR: In this paper, an integrated quantum photonic circuit that can be thermally reconfigured has been fabricated by femtosecond laser micromachining, which can be used as a building block for reconfigurable quantum circuits.
Abstract: The importance of integrated quantum photonics in the telecom band is based on the possibility of interfacing with the optical network infrastructure that was developed for classical communications. In this framework, femtosecond laser-written integrated photonic circuits, which have already been assessed for use in quantum information experiments in the 800-nm wavelength range, have great potential. In fact, these circuits, being written in glass, can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers, which is a key requirement for a low-loss processing node in future quantum optical networks. In addition, for several applications, quantum photonic devices must be dynamically reconfigurable. Here, we experimentally demonstrate the high performance of femtosecond laser-written photonic circuits for use in quantum experiments in the telecom band, and we demonstrate the use of thermal shifters, which were also fabricated using the same femtosecond laser, to accurately tune such circuits. State-of-the-art manipulation of single- and two-photon states is demonstrated, with fringe visibilities greater than 95%. The results of this work open the way to the realization of reconfigurable quantum photonic circuits based on this technological platform. An integrated quantum photonic circuit that can be thermally reconfigured has been fabricated by femtosecond laser micromachining. Thermally reconfigurable quantum photonic circuits would permit quantum protocols to be implemented that require dynamically changing circuit functionality. A team in Italy has used femtosecond laser micromachining to inscribe waveguide Mach–Zehnder interferometers that operate at telecommunication wavelengths on a glass chip and also to pattern gold resistive heaters on the chip surface, which can be used to accurately tune the circuit. The researchers demonstrated high-quality manipulation of single- and two-photon states with fringe visibilities exceeding 95%. They also fully characterized the thermal response of the interferometric circuit and found good agreement with that expected based on the fabrication design. This device could potentially be used as a building block for reconfigurable quantum circuits.
TL;DR: Viscous sample delivery that decreases the net protein consumed in serial femtosecond crystallography is described, which has a low background, is compatible with membrane proteins and can be used at a wide range of temperatures.
TL;DR: In this paper, laser-induced periodic surface structures (LIPSS, ripples) were processed on steel (X30CrMoN15-1) and titanium (Ti) surfaces by irradiation in air with linear polarized femtosecond laser pulses with a pulse duration of 30 f at 790 nm wavelength.
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TL;DR: In this paper, the authors proposed a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation.
Abstract: We propose a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photo-injection of dense (>10^20 cm^-3) electron-hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows to manipulate by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20 % tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such single-particle nanodevice enables to design fast and ultracompact optical switchers and modulators.
TL;DR: Results open up the way towards femtosecond time-resolved experiments using high harmonics exploiting the powerful element-sensitive XMCD effect and resolving the ultrafast magnetization dynamics of individual components in complex materials.
Abstract: Recent advances in high-harmonic generation gave rise to soft X-ray pulses with higher intensity, shorter duration and higher photon energy One of the remaining shortages of this source is its restriction to linear polarization, since the yield of generation of elliptically polarized high harmonics has been low so far We here show how this limitation is overcome by using a cross-polarized two-colour laser field With this simple technique, we reach high degrees of ellipticity (up to 75%) with efficiencies similar to classically generated linearly polarized harmonics To demonstrate these features and to prove the capacity of our source for applications, we measure the X-ray magnetic circular dichroism (XMCD) effect of nickel at the M2,3 absorption edge around 67 eV There results open up the way towards femtosecond time-resolved experiments using high harmonics exploiting the powerful element-sensitive XMCD effect and resolving the ultrafast magnetization dynamics of individual components in complex materials
TL;DR: In this paper, a femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering in complex oxide heterostructures.
Abstract: Static strain in complex oxide heterostructures1, 2 has been extensively used to engineer electronic and magnetic properties at equilibrium3. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across heterointerfaces dynamically4. Here, by exciting large-amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a heterointerface. Femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering. We observe a magnetic melt front that propagates from the substrate interface into the film, at a speed that suggests electronically driven motion. Light control and ultrafast phase front propagation at heterointerfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices.
TL;DR: In this paper, a femtosecond (fs) laser ablation aided tomography at the mm{sup 3}-scale is demonstrated at sub-diffraction limit resolution.
TL;DR: In this article, a switchable underwater superoleophobicity on femtosecond laser-induced rough TiO2 surfaces by alternate UV irradiation and dark storage is achieved for the first time.
Abstract: Switchable underwater superoleophobicity–superoleophilicity on femtosecond laser-induced rough TiO2 surfaces by alternate UV irradiation and dark storage is achieved for the first time. Femtosecond laser ablation not only forms a micro/nanoscale hierarchical rough structure but also oxidizes the Ti materials, resulting in a rough TiO2 layer covering on the surface. The reversible switching of underwater oil wettability is caused by photoinduced switching between superhydrophobic and superhydrophilic states in air. These rough TiO2 surfaces can even respond to visible light. We believe this subtle switching method will be potentially applied in the biological and medical fields.
TL;DR: Four typical aspects of femtosecond laser induced special wettable: superhydrophobicity, underwater superoleophobicity, anisotropic wettability, and smart wettabilities are introduced.
Abstract: Femtosecond laser microfabrication is emerging as a hot tool for controlling the wettability of solid surfaces. This paper introduces four typical aspects of femtosecond laser induced special wettability: superhydrophobicity, underwater superoleophobicity, anisotropic wettability, and smart wettability. The static properties are characterized by the contact angle measurement, while the dynamic features are investigated by the sliding behavior of a liquid droplet. Using different materials and machining methods results in different rough microstructures, patterns, and even chemistry on the solid substrates. So, various beautiful wettabilities can be realized because wettability is mainly dependent on the surface topography and chemical composition. The distinctions of the underlying formation mechanism of these wettabilities are also described in detail.