Cascaded Nondegenerate Four-Wave Mixing Technique for High-Power Single-Cycle Pulse Synthesis in the Visible and Ultraviolet Ranges

We present a new technique to synthesize high-power single-cycle pulses in the visible and ultraviolet ranges by coherent superposition of a multiband octave-spanning spectrum obtained by highly-nondegenerate cascaded four-wave mixing of femtosecond pulses in bulk isotropic nonresonant media. The generation of coherent spectra spanning over two octaves in bandwidth is experimentally demonstrated using a thin fused silica slide. Full characterization of the intervening multicolored fields using frequency-resolved optical gating, where multiple cascaded orders have been measured simultaneously for the first time, supports the possibility of direct synthesis of near-single-cycle 2.2 fs visible-UV pulses without recurring to complex amplitude or phase control, which should enable many applications in science and technology.Comment: 13 pages, 4 figures. Submitted to Physical Review

Self-calibrating d-scan: measuring ultrashort laser pulses on-target using an arbitrary pulse compressor

In most applications of ultrashort pulse lasers, temporal compressors are used to achieve a desired pulse duration in a target or sample, and precise temporal characterization is important. The dispersion-scan (d-scan) pulse characterization technique usually involves using glass wedges to impart variable, well-defined amounts of dispersion to the pulses, while measuring the spectrum of a nonlinear signal produced by those pulses. This works very well for broadband few-cycle pulses, but longer, narrower bandwidth pulses are much more difficult to measure this way. Here we demonstrate the concept of self-calibrating d-scan, which extends the applicability of the d-scan technique to pulses of arbitrary duration, enabling their complete measurement without prior knowledge of the introduced dispersion. In particular, we show that the pulse compressors already employed in chirped pulse amplification (CPA) systems can be used to simultaneously compress and measure the temporal profile of the output pulses on-target in a simple way, without the need of additional diagnostics or calibrations, while at the same time calibrating the often-unknown differential dispersion of the compressor itself. We demonstrate the technique through simulations and experiments under known conditions. Finally, we apply it to the measurement and compression of 27.5 fs pulses from a CPA laser.Comment: 11 pages, 5 figures, Scientific Reports, in pres

Results for Channel Error Profiles for DECT

This letter presents the main statistical characterization of the underlying error process obtained in the case of the Digital European Cordless Telecommunications (DECT) radio system. By simulation of the transmission link, error sequences are generated for different channel parameters. Relevant statistics are then computed for the purpose of efficient channel coding design and evaluation

"The Role of International Technological Spillovers in the Economic Growth of the OECD Countries "

This paper explores the role of imports as a mechanism of transmission of international technological spillovers and the significance of these for the growth and economic convergence of the OECD countries. For this purpose a growth model is estimated that includes amongst its determinants a measure of the stock of technological knowledge. The results reveal first that international technological spillovers transmitted through imports have had a favourable influence on the economic growth of the OECD countries, Secondly, they suggest that the capacity of countries to take advantage of those spillovers depend on their own human and R&D capital endowments..

Probing halo nucleus structure through intermediate energy elastic scattering

This work addresses the question of precisely what features of few body models of halo nuclei are probed by elastic scattering on protons at high centre-of-mass energies. Our treatment is based on a multiple scattering expansion of the proton-projectile transition amplitude in a form which is well adapted to the weakly bound cluster picture of halo nuclei. In the specific case of $^{11}$Li scattering from protons at 800 MeV/u we show that because core recoil effects are significant, scattering crosssections can not, in general, be deduced from knowledge of the total matter density alone. We advocate that the optical potential concept for the scattering of halo nuclei on protons should be avoided and that the multiple scattering series for the full transition amplitude should be used instead.Comment: 8 pages REVTeX, 1 eps figure, accepted for publication in Phys. Rev.

Spitzer/IRS investigation of MIPSGAL 24 microns compact bubbles

The MIPSGAL 24 $\mu$m Galactic Plane Survey has revealed more than 400 compact-extended objects. Less than 15% of these MIPSGAL bubbles (MBs) are known and identified as evolved stars. We present Spitzer observations of 4 MBs obtained with the InfraRed Spectrograph to determine the origin of the mid-IR emission. We model the mid-IR gas lines and the dust emission to infer physical conditions within the MBs and consequently their nature. Two MBs show a dust-poor spectrum dominated by highly ionized gas lines of [\ion{O}{4}], [\ion{Ne}{3}], [\ion{Ne}{5}], [\ion{S}{3}] and [\ion{S}{4}]. We identify them as planetary nebulae with a density of a few 10$^3\ \rm{cm^{-3}}$ and a central white dwarf of $\gtrsim 200,000$ K. The mid-IR emission of the two other MBs is dominated by a dust continuum and lower-excitation lines. Both of them show a central source in the near-IR (2MASS and IRAC) broadband images. The first dust-rich MB matches a Wolf-Rayet star of $\sim 60,000$ K at 7.5 kpc with dust components of $\sim170$ and $\sim1750$ K. Its mass is about $10^{-3}\ \rm{M_\odot}$and its mass loss is about$10^{-6}\ \rm{M_\odot/yr}. The second dust-rich MB has recently been suggested as a Be/B[e]/LBV candidate. The gas lines of [\ion{Fe}{2}] as well as hot continuum components (\sim300$and$\sim1250$K) arise from the inside of the MB while its outer shell emits a colder dust component ($\sim75$K). The distance to the MB remains highly uncertain. Its mass is about$10^{-3}\ \rm{M_\odot}$and its mass loss is about$10^{-5}\ \rm{M_\odot/yr}$.Comment: accepted for publication in Ap