Processing of materials by ultrashort laser pulses has evolved significantly over the last decade and is starting to reveal its scientific, technological and industrial potential. In ultrafast laser manufacturing, optical energy of tightly focused femtosecond or picosecond laser pulses can be delivered to precisely defined positions in the bulk of materials via two-/multi-photon excitation on a timescale much faster than thermal energy exchange between photoexcited electrons and lattice ions. Control of photo-ionization and thermal processes with the highest precision, inducing local photomodification in sub-100-nm-sized regions has been achieved. State-of-the-art ultrashort laser processing techniques exploit high 0.1–1 μm spatial resolution and almost unrestricted three-dimensional structuring capability. Adjustable pulse duration, spatiotemporal chirp, phase front tilt and polarization allow control of photomodification via uniquely wide parameter space. Mature opto-electrical/mechanical technologies have enabled laser processing speeds approaching meters-per-second, leading to a fast lab-to-fab transfer. The key aspects and latest achievements are reviewed with an emphasis on the fundamental relation between spatial resolution and total fabrication throughput. Emerging biomedical applications implementing micrometer feature precision over centimeter-scale scaffolds and photonic wire bonding in telecommunications are highlighted.

We demonstrate the possibility to achieve optical triggering of photochemical reactions via two-photon absorption using incoherent light sources. This is accomplished by the use of arrays of gold nanoparticles, specially tailored with high precision to obtain high near-field intensity enhancement.

Studies on two-photon lithography in negative SU-8 photoresist demonstrate the possibility of obtaining mechanically stable, stress-free, extended nanorods having lateral sizes of about 30 nm (corresponding to λ/25 resolution). The high resolution achievable with the given combination of materials and fabrication techniques demonstrates its potential for the fabrication of large-scale nanostructures, such as photonic crystals with photonic stop gaps at visible wavelengths.

Modification of optical properties of materials by nanoengineering is one of the current trends in the materials science. Periodic dielectric and metallo-dielectric nanostructures show great potential for the control of light emission, propagation and absorption via photonic band-gap effect. [1,2] Nanoengineered particles of noble metals exhibit intense optical nearfield due to localized surface plasmon (LSP) resonance and promise novel applications in nonlinear optics and spectroscopy, [3,4] optical sensing, [5][6][7][8][9] and metrology. [10,11] Although metals are typically perceived as poor light emitters, silver and gold nanoparticles exhibit intense photoluminescence (PL) under near-infrared excitation via two-photon absorption (TPA) assisted by the strong LSP near-field.[12] Thus, structurally tailored metal nanoparticles can be regarded as an alternative to chemically tailored [13][14][15] organic molecules optimized for high TPA (and PL) rates for applications in highresolution three-dimensional fluorescence imaging [16] and single-molecule fluorescence-quenching spectroscopy.[17]However, such structural tailoring requires control of the nanoparticles' size, shape and orientation with nanometric accuracy. Although fabrication techniques having an adequate resolution have been available in semiconductor nanotechnology, most of the earlier studies focused on nanoparticles fabricated by chemical techniques. This approach produces ensembles of nanoparticles having significant variations of size, shape, and orientation, which may have deteriorating effect on the ensemble-averaged optical and near-field characteristics. Here we describe large, homogeneous clusters of gold nanoblocks, fabricated using electron-beam lithography (EBL) and vacuum deposition techniques, whose high degree of homogeneity allows observation of strong PL excited via TPA at near-infrared wavelengths. The key feature of our structures is intense near-field existing in few nanometer-wide nanogaps between the nanoblocks, and associated with collective LSP modes of the cluster. The degree of localization of these modes, and correspondingly, the PL intensity can be tuned by fine adjustment of the nanogap width. Thus, gold nanoengineering by a top-down technology allows one to obtain metallic systems capable of light emission, and having controllable TPA and PL properties.Photoluminescence from gold is due to radiative recombination following interband electronic transitions between the d and sp electronic bands. [12,18,19] Gold nanoparticles and rough surfaces exhibit PL quantum yields over a million times larger than the bulk gold [20] due to local enhancement of the LSP near-field [21] by orders of magnitude, compared to the incident radiation. Closely-spaced nanoparticles usually exhibit collective LSP modes whose field enhancement is even higher than that of non-interacting nanoparticles, and increases with decreasing interparticle separation. [22] Maximizing the PL yield will likely require gaps between the particles smaller than 20 nm ...

ring under atmospheric conditions. TEA (2.2 mL, 99+ %) was slowly added drop by drop to the solution under agitation. After 30±45 min stirring the white product was filtered off, washed with DMF, and was finally dried at 373 K for 3±5 h in an oven. After drying the yield was 71 % in weight with respect to zinc nitrate. The same synthesis was repeated adding three drops of H 2 O 2 (35 %) to the DMF solution containing dissolved BDC and zinc nitrate and then the TEA was added directly to the solution.For the second synthesis, which did not produce pure MOF-5, 0.3 g of Zn(NO 3 ) 2 . xH 2 O and 0.227 g of BDC were dissolved in 10 mL of DMF and 2.4 mL of chlorobenzene (99.7 %, also purchased from Alfa Aesar), and three droops of H 2 O 2 were added. The vessel containing the reagent solution was put into a larger closed vessel containing 2 mL of TEA. After one week, the white crystalline product at the interface between the air and solution was filtered off and washed with DMF and then dried for 3±5 h at 373 K.Characterization: Powder X-ray diffraction data were recorded for the as-synthesized and dried sample with a Siemens D5000 powder diffractometer using Cu Ka radiation and a secondary monochromator.Images of MOF-5 crystals were taken with a SEM and with a fieldemission SEM.The specific surface area (SSA) and pore size of the samples were investigated with a quantachrome Autosorb automated gas sorption apparatus using N 2 gas. To measure the SSA, the solvent incorporated in the crystalline structure during the synthesis was completely removed by heating at 473 K under a vacuum of 10 ±6 mbar. Hydrogen-Storage Measurements: For hydrogen-storage measurements we used a volumetric setup that had been previously tested both for room-temperature measurements, using well-known metal hydrides, and at 77 K, using activated carbon.For adsorption measurements at room temperature, the experimental set-up was immersed in a temperature-controlled water bath at 298 K. High purity (99.999 %) hydrogen gas was introduced into a reservoir of known volume and, after thermal equilibrium had been achieved, the gas was permitted to expand into the sample holder.For measurements at 77 K, the sample holder was immersed in liquid nitrogen and the pressure drop due to cooling and to enhanced hydrogen storage was recorded. To calculate the storage capacity of the sample, the experiment was repeated accurately under the same conditions for a blind sample (sea sand) of the same volume, which does not adsorb any hydrogen. The difference in hydrogen pressure drop is attributed exclusively to hydrogen storage.After every adsorption step, the sample was heated under vacuum and the measurement was repeated for a new hydrogen pressure. This procedure ensured that every adsorption value was measured independently from the previous one. The experiment was been performed a second time using a different sample mass. The congruency in the measured storage values for the two experiments was additional evidence of the high accuracy of our measuring system. T...

At extreme pressures and temperatures, such as those inside planets and stars, common materials form new dense phases with compacted atomic arrangements and unusual physical properties. The synthesis and study of new phases of matter at pressures above 100 GPa and temperatures above 104 K—warm dense matter—may reveal the functional details of planet and star interiors, and may lead to materials with extraordinary properties. Many phases have been predicted theoretically that may be realized once appropriate formation conditions are found. Here we report the synthesis of a superdense stable phase of body-centred-cubic aluminium, predicted by first-principles theories to exist at pressures above 380 GPa. The superdense Al phase was synthesized in the non-equilibrium conditions of an ultrafast laser-induced microexplosion confined inside sapphire (α-Al2O3). Confined microexplosions offer a strategy to create and recover high-density polymorphs, and a simple method for tabletop study of warm dense matter.

Femtosecond laser fabrication of three-dimensional structures for photonics applications is reviewed. Fabrication of photonic crystal structures by direct laser writing and holographic recording by multiple beam interference techniques are discussed. The physical mechanisms associated with structure formation and postfabrication are described. The advantages and limitations of various femtosecond laser microfabrication techniques for the preparation of photonic crystals and elements of microelectromechanical and micro-optofluidic systems are discussed.

Femtosecond laser pulses are useful for laser microfabrication through multiphoton absorption. However, it is difficult to create interference of femtosecond pulses for the fabrication of periodic structures. In this letter, we report the fabrication of two-dimensional periodic structures by means of multibeam interference of femtosecond pulses. Scanning electron microscopy revealed a rod structure arranged into a square lattice. The possibility of controlling the period of the lattice, rod thickness, and rod shape were demonstrated.