The direct evaluation of attosecond chirp from a streaking measurement

We derive an analytical expression, from classical electron trajectories in a laser field, that relates the breadth of a streaked photoelectron spectrum to the group-delay dispersion of an isolated attosecond pulse. Based on this analytical expression, we introduce a simple, efficient and robust procedure to instantly extract the attosecond pulse's chirp from the streaking measurement.Comment: 4 figure

High-order harmonic generation with a strong laser field and an attosecond-pulse train: the Dirac Delta comb and monochromatic limits

In recent publications, it has been shown that high-order harmonic generation can be manipulated by employing a time-delayed attosecond pulse train superposed to a strong, near-infrared laser field. It is an open question, however, which is the most adequate way to approximate the attosecond pulse train in a semi-analytic framework. Employing the Strong-Field Approximation and saddle-point methods, we make a detailed assessment of the spectra obtained by modeling the attosecond pulse train by either a monochromatic wave or a Dirac-Delta comb. These are the two extreme limits of a real train, which is composed by a finite set of harmonics. Specifically, in the monochromatic limit, we find the downhill and uphill sets of orbits reported in the literature, and analyze their influence on the high-harmonic spectra. We show that, in principle, the downhill trajectories lead to stronger harmonics, and pronounced enhancements in the low-plateau region. These features are analyzed in terms of quantum interference effects between pairs of quantum orbits, and compared to those obtained in the Dirac-Delta limit.Comment: 10 pages, 7 figures (eps files). To appear in Laser Physic

Responsibility & Risk: Operationalizing comprehensive climate risk layering in Austria among multiple actors (RESPECT)

Damages caused by climate and weather extremes, such as floods and droughts, have increased over the last few decades and will likely broaden with the progression of climate change and socioeconomic development. Such climate-related risks are already being governed within the framework of natural disaster risk management, as well as climate change adaptation. However, to manage these climate risks more effectively it is necessary to link these two domains under the umbrella of Climate Risk Management (CRM)

Near-field microwave techniques for micro – and nano - scale characterization in materials science

In this paper, the basic principles of Near-Field Microscopy will be reviewed with focus on the micro- and nano-scale resolution configurations for material science measurements. Results on doping profile, dielectric and magnetic properties will be presented, with details on the calibration protocols needed for quantitative estimation of the dielectric constant and of the permeability

Subcycle controlled charge-directed reactivity with few-cycle midinfrared pulses

The steering of electron motion in molecules is accessible with waveform- controlled few-cycle laser light and may control the outcome of light-induced chemical reactions. An optical cycle of light, however, is much shorter than the duration of the fastest dissociation reactions, severely limiting the degree of control that can be achieved. To overcome this limitation, we extended the control metrology to the midinfrared studying the prototypical dissociative ionization of D2 at 2.1  μm. Pronounced subcycle control of the directional D+ ion emission from the fragmentation of D+2 is observed, demonstrating unprecedented charge-directed reactivity. Two reaction pathways, showing directional ion emission, could be observed and controlled simultaneously for the first time. Quantum-dynamical calculations elucidate the dissociation channels, their observed phase relation, and the control mechanisms

Nondestructive imaging of atomically thin nanostructures buried in silicon

It is now possible to create atomically thin regions of dopant atoms in silicon patterned with lateral dimensions ranging from the atomic scale (angstroms) to micrometers. These structures are building blocks of quantum devices for physics research and they are likely also to serve as key components of devices for next-generation classical and quantum information processing. Until now, the characteristics of buried dopant nanostructures could only be inferred from destructive techniques and/or the performance of the final electronic device; this severely limits engineering and manufacture of real-world devices based on atomic-scale lithography. Here, we use scanning microwave microscopy (SMM) to image and electronically characterize three-dimensional phosphorus nanostructures fabricated via scanning tunneling microscope–based lithography. The SMM measurements, which are completely nondestructive and sensitive to as few as 1900 to 4200 densely packed P atoms 4 to 15 nm below a silicon surface, yield electrical and geometric properties in agreement with those obtained from electrical transport and secondary ion mass spectroscopy for unpatterned phosphorus δ layers containing ~1013 P atoms. The imaging resolution was 37 ± 1 nm in lateral and 4 ± 1 nm in vertical directions, both values depending on SMM tip size and depth of dopant layers. In addition, finite element modeling indicates that resolution can be substantially improved using further optimized tips and microwave gradient detection. Our results on three-dimensional dopant structures reveal reduced carrier mobility for shallow dopant layers and suggest that SMM could aid the development of fabrication processes for surface code quantum computers.ISSN:2375-254

Propagation-enhanced generation of intense high-harmonic continua in the 100-eV spectral region

The study of core electron dynamics through nonlinear spectroscopy requires intense isolated attosecond extreme ultraviolet or even X-ray pulses. A robust way to produce these pulses is high-harmonic generation (HHG) in a gas medium. However, the energy upscaling of the process depends on a very demanding next-generation laser technology that provides multi-terawatt (TW) laser pulses with few-optical-cycle duration and controlled electric field. Here, we revisit the HHG process driven by 16-TW sub-two-cycle laser pulses to reach high intensity in the 100-eV spectral region and beyond. We show that the combination of above barrier-suppression intensity with a long generation medium significantly enhances the isolation of attosecond pulses compared to lower intensities and/or shorter media and this way reduces the pulse duration as well as field-stability requirements on the laser driver. This novel regime facilitates the real-time observation of electron dynamics at the attosecond timescale in atoms, molecules, and solids