There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire (NW) arrays. The aligned NWs are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the NW as a result of its bending. The rectifying characteristic of the Schottky barrier formed between the metal tip and the NW leads to electrical current generation. The efficiency of the NW-based piezoelectric power generator is estimated to be 17 to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.

/pdf/piezoelectric-nanogenerators-based-on-zinc-oxide-nanowire-1swcm3u2x8.pdf

Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays

Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference in the amplitudes of optical transitions. In this way the optical properties of a medium can be dramatically modified, leading to electromagnetically induced transparency and related effects, which have placed gas-phase systems at the center of recent advances in the development of media with radically new optical properties. This article reviews these advances and the new possibilities they offer for nonlinear optics and quantum information science. As a basis for the theory of electromagnetically induced transparency the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser. They then discuss pulse propagation and the adiabatic evolution of field-coupled states and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments. The extension of these concepts to very weak optical fields in the few-photon limit is then examined. The review concludes with a discussion of future prospects and potential new applications.

/pdf/electromagnetically-induced-transparency-optics-in-coherent-2dhges92td.pdf

Electromagnetically induced transparency : Optics in coherent media

Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

https://science.sciencemag.org/content/sci/299/5605/358.full.pdf

Photonic crystal fibers

Aperiodic XUV multilayer coatings with broad spectral bandwidth and flat dispersion characteristics have been developed and fabricated as reflecting and spectrally filtering optical elements for attosecond XUV pulses. Based on a genetic computational optimization algorithm aperiodic Mo/Si multilayer structures exhibiting up to 40 eV spectral bandwidth and pulse responses down to about 100 attoseconds at 80 eV center photon energy could be simulated. An experimental multilayer design exhibiting about 15 eV spectral bandwidth at 93 eV photon energy was realized and tested in an attosecond XUV pump – IR probe photoionization experiment (attosecond streak camera) utilizing single attosecond pulses from a High Harmonic Generation source. The results display the enhanced spectral bandwidth filtered by the aperiodic mirror which holds the potential for the extraction of single XUV pulses shorter than 200 attoseconds.

Chirped Multilayer Soft X-Ray Mirrors for Attosecond Soft X-Ray Pulses

A 1-MW, sub-10-fs T i:sapphire oscillator

Since its discovery in 1982 by L'Huillier and coworkers [1], non-sequential double ionization (NSDI) of atoms in strong laser fields has been the subject of numerous experimental and theoretical studies. Yet, the mechanisms that govern this process are not fully understood. Advances in ultra-fast laser technology have permitted the generation of light pulses with durations close to a single optical cycle [2], which can be used to study quantum dynamics with attosecond time resolution. Using a reaction microscope (REMI) in combination with the recently developed single-shot carrier-envelope phase (CEP) measurement technique [3], we investigate the sub-cycle dynamics of the NSDI process in argon and neon atoms exposed to near single-cycle laser pulses.

Sub-cycle double ionization dynamics of argon and neon

Snb-10O-fs klla-repetitioii-rate ainpliliers combine the benefits of high peak powers with the possibility of using sensitive signal-averaging tecliniques. The technique of chirped pulsc aniplification (CPA) led to significarit progress i n the amplification of femtosecond pulses. llecent advances resulted i n the generation of optical pulses of 30 Is duration a t the TW level a t a repetition rate of 10 I I z . ' . ~ A t klIz repetition rates pJ-energy 304s (Ref. 131) and 0.9-mJ 214s pulses4 have recently been reported. Uoth results have been achieved by using complex and lossy grating-based pulse stretching systems. In this contribution we report for what we believe is the first time on the generation of sub-mJ-energy femtosecond pulses without using a pulse stretcher. We have developed a compact eight-pass Ti:S amplifer, which is seeded with -10 Is, 100nm-bandwidth pulses (@ 800nm) from a mirror-dispersion-controlled Ti:S oscillator. The system can be safely operated without an additional stretcher because the pulse broadening introduced by the pulse slicing and isolation components is sufficient to prevent nonlinear effects and damage in the amplifier crystal. In contrast with the conventional approach, pulse selection by a Pockels cell is performed only after the full 8O-MHz pulse train passed through the amplifier crystal four times. In this manner, ASE could be dramatically suppressed as compared to previously reported results.' Carefully placed apertures prevent the high-gain amplifier setup from lasing. After amplification the chirped pulses are recompressed in a setup consisting of dispersive mirrors and a low-dispersion FK5 (Schott) prism pair, resulting i n a quartic-phase-limited amplifier system.

Sub-mJ., Sub-20-fs Pulses from Ti:sapphire without Using a Pulse Stretcher

In recent years technologies were developed to generate pulses shorter than 5 fs and consisting of less than two optical cycles in full-width at half maximum (few-cycle pulses). The (quite often extremely) nonlinear interaction of such pulses with matter renders important only one or a fraction of one optical cycle. In recent months it became possible to stabilize the phase of the carrier with respect to the pulse envelope (“absolute” phase) for powerful few-cycle pulses. Almost at the same time the absolute phase has been measured and controlled thus tailoring the temporal evolution of single optical cycles. First experiments investigating photoionization were performed and showed a wealth of information inaccessible so far.

Ferenc Krausz

Papers

Chirped Multilayer Soft X-Ray Mirrors for Attosecond Soft X-Ray Pulses

A 1-MW, sub-10-fs T i:sapphire oscillator

Sub-cycle double ionization dynamics of argon and neon

Sub-mJ., Sub-20-fs Pulses from Ti:sapphire without Using a Pulse Stretcher

Quantum Optics with Single Optical Cycles