Owing to the kinetic nature of the glass transition, the ability to significantly alter the properties of amorphous solids by the typical routes to the vitreous state is restricted. For instance, an order of magnitude change in the cooling rate merely modifies the value of the glass transition temperature (T(g)) by a few degrees. Here we show that matrix-assisted pulsed laser evaporation (MAPLE) can be used to form ultrastable and nanostructured glassy polymer films which, relative to the standard poly(methyl methacrylate) glass formed on cooling at standard rates, are 40% less dense, have a 40 K higher T(g), and exhibit a two orders of magnitude enhancement in kinetic stability at high temperatures. The unique set of properties of MAPLE-deposited glasses may make them attractive in technologies where weight and stability are central design issues.

The enhancement of stimulated Raman backscattering (SRBS) amplification was demonstrated by introducing a plasma density gradient along the pump and the seed interaction path and by a novel double-pass design. The energy transfer efficiency was significantly improved to a level of 6.4%. The seed pulse was amplified by a factor of more than 20 000 from the input in a 2mm long plasma, which also exceeded the intensity of the pump pulse by 2 orders of magnitude. This was accompanied by very effective pulse compression, from 500fsto90fs in the first pass measurements and in the second pass down to approximately 50fs, as it is indicated by the energy-pulse duration relation. Further improvements to the energy transfer efficiency and the SRBS performance by extending the region of resonance is also discussed where a uniform ∼4mm long plasma channel for SRBS was generated by using two subsequent laser pulses in an ethane gas jet.

A plasma-based resonant backward Raman amplifier/compressor for high power amplification of short laser pulses might, under ideal conditions, convert as much as 90% of the pump energy to the seed pulse. While the theoretical highest possible efficiency of this scheme has not yet been achieved, larger efficiencies than ever before obtained experimentally (6.4%) are now being reported, and these efficiencies are accompanied by strong pulse compression. Based on these recent extensive experiments, it is now possible to deduce that the experimentally realized efficiency of the amplifier is likely constrained by two factors, namely the pump chirp and the plasma wavebreaking, and that these experimental observations may likely involve favorable compensation between the chirp of the laser and the density variation of the mediating plasma. Several methods for further improvement of the amplifier efficiency in current experiments are suggested.

The development of a facile method for fabricating one-dimensional, precisely positioned nanostructures over large areas offers exciting opportunities in fundamental research and innovative applications. Large-scale nanofabrication methods have been restricted in accessibility due to their complexity and cost. Likewise, bottom-up synthesis of nanowires has been limited in methods to assemble these structures at precisely defined locations. Nanomaterials such as PbZr x Ti1−x O3 (PZT) nanowires (NWs)which may be useful for nonvolatile memory storage (FeRAM), nanoactuation, and nanoscale power generationare difficult to synthesize without suffering from polycrystallinity or poor stoichiometric control. Here, we report a novel fabrication method which requires only low-resolution photolithography and electrochemical etching to generate ultrasmooth NWs over wafer scales. These nanostructures are subsequently used as patterning templates to generate PZT nanowires with the highest reported piezoelectric performance (d eff ∼ 145 pm/V). The combined large-scale nanopatterning with hierarchical assembly of functional nanomaterials could yield breakthroughs in areas ranging from nanodevice arrays to nanodevice powering.

Coherent intense attosecond X-ray pulses could lead to a fast dynamical imaging of the biological macromolecules and other material nanostructures with a unique combination of a record high temporal and spatial resolution. Plasma based X-rays laser sources are capable to produce high energy X-ray pulses but with relatively long picosecond duration. The sources based on high-harmonic generation (HHG) of a laser field allow to produce much shorter pulses but of lower energy. We suggest two different paths towards intense sub-femtosecond X-ray sources, namely i) via efficient transformation of the picosecond radiation of the X-ray plasma lasers into the trains of sub-femtosecond pulses in a resonantly absorbing medium, and ii) via amplification of HHG radiation in the active medium of the X-ray plasma lasers. We show that essentially the same technique can be used for realization of both paths. This technique is a modulation of the parameters of the resonant transition (accordingly in absorbing or amplifying medium) produced under the action of sufficiently strong infrared or optical field. We propose experimental realization of the suggested technique in the passive/active media of i) Li III ions modulated by the mid-IR laser field and ii) C VI ions modulated by the optical laser radiation. I.

Experimental evidences of Raman amplification of ultrashort pulses in microcapillary plasmas are presented. The amplification of 100-500 fs pulses was investigated in microcapillaries with different lengths. The experimental data, together with simulation results, indicate that the resonance condition for Raman amplification in high-density plasma, n(e) approximately 1-3x10(20) cm(-3), existed only in a very short plasma column. Such an assumption makes it possible to reconcile the experimental results and theoretical predictions. Investigations in very short microcapillaries (0.2-0.5 mm) with a broadband seed pulse further support this hypothesis and the amplification factor is in agreement with the linear growth rate.

Raman amplification is a resonant process in which the energy of a long pump pulse is transferred to a short seed pulse by a plasma wave. There has been a significant effort to identify a window in parameter space within which the interaction is expected to be highly efficient and not degraded by competing instabilities or excessive damping. However, experimental results have thus far failed to approach the theoretical limits. Recent amplified signal spectra display a characteristic blue shift, which evolves within the seed pulse duration and suggests that the mechanism responsible for this shift is also limiting amplification in these experiments. We present the evidence and explore different hypotheses for the origins of the shift—namely localization in density minima along the axis of laser propagation induced by an ion acoustic wave that could arise from the Langmuir decay instability, filamentation which could also modulate the plasma density but in the plane transverse to laser propagation, particle trapping, and additional ionization induced by the amplified seed field.

In a Raman plasma amplifier, the aim is to create plasma conditions in which Raman backscattering is the fastest growing instability, outrunning all competing effects so that it is possible to amplify and compress a laser beam to unprecedented unfocused intensities by utilizing that instability. However, achieving high efficiencies via this scheme has proven very difficult experimentally. Recent data show the simultaneous occurrence of stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and stimulated electron-acoustic scattering (SEAS). The appearance of SEAS is indicative of strong particle trapping, the existence of which is hard to justify without highlighting the interplay between SRS and SBS.