Search results for "PUMP"

Lorenz character of the Doppler-broadened far-infrared laser

1991

The dynamic behavior of an optically pumped Doppler-broadened single-mode far-infrared laser is theoretically investigated in detail and compared with that of the simpler Lorenz–Haken laser. Through the analysis of phase diagrams, three-dimensional attractor’s projections, intensity maps, and the different terms of the laser equations, the analogies and the differences between the two models are determined. Optical pumping and Doppler broadening, present in this far-infrared laser model, can be approximately incorporated into a Lorenz–Haken model with effective parameters. These results represent a further step toward the understanding of the Lorenz-like behavior observed in recent years in…

High performance configuration of all-raman N × 40 Gbit/s RZ-DPSK systems over ultrawave<sup>TM</sup> maps

2007

In order to explore the impact of the DPSK format on best system configuration, and to cross-check the simulation tools, transmission experiments involving 16 × 40 Gbit/s WDM channels on a recirculating loop including a symmetric UltrawaveTM fiber dispersion map are performed. In these experiments the RZ-DPSK format is used, and each 100 km span is brought to optical transparency with 75%(25%) of backward (forward) Raman gain. The pre-compensation is experimentally varied, and a significant transmission improvement after 4000 km for the pre-compensation of -350 ps/nm is observed.

Counter-propagating difference frequency mixing in diamond with terahertz waves

2013

We investigate four-wave mixing between terahertz and optical pulses in diamond. We observe the occurrence of sum and difference frequency generation, with the latter being phase-matched for terahertz pulses counter-propagating to the optical field.

Realization of a robust single-parameter quantized charge pump

2008

This paper describes a novel scheme for quantized charge pumping based on single-parameter modulation. The device is realized in an AlGaAs-GaAs gated nanowire. A particular advantage of this realization is that operation in the quantized regime can be achieved in a potentially large range of amplitude and dc off-set of the driving signal. This feature together with the simple configuration might enable large scale parallel operation of many such devices.

Nonlinear effects in optical pumping of a cold and slow atomic beam

2015

By photoionizing hyperfine (HF) levels of the Cs state $6{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around $180\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s})$ spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The ev…

Polarization-sensitive population trapping in an optically pumped laser

1994

Optical pumping and unstable nuclei

1985

The paper reviews the application of optical pumping to short-lived nuclei, where either the nuclear polarisation is detected by the β-decay asymmetry or the atomic polarisation by Stern-Gerlach-analyzer. Moreover the paper deals with collinear laser spectroscopy on beams of short-lived, mass-separated isotopes. The aim of the experiments is the systematic investigation of nuclear structure through the determination of spin, moments and charge radii from the hyperfine structure and isotopic shift of the atomic spectra. The impact of these experiments on the theory of nuclear forces and structure is discussed by means of a few examples.

Disentangling size effects and spectral inhomogeneity in carbon nanodots by ultrafast dynamical hole-burning.

2018

Carbon nanodots (CDs) are a novel family of nanomaterials exhibiting unique optical properties. In particular, their bright and tunable fluorescence redefines the paradigm of carbon as a "black" material and is considered very appealing for many applications. While the field keeps growing, understanding CDs fundamental properties and relating them to their variable structures becomes more and more critical. Two crucial problems concern the effect of size on the electronic structure of CDs, and to what extent their optical properties are influenced by structural disorder. Furthermore, it remains largely unclear whether traditional concepts borrowed from the photo-physics of semiconductor qua…

The Neochord Procedure After Failed Surgical Mitral Valve Repair.

2021

Surgical mitral valve reintervention is associated with significant morbidity and mortality, and repeat repair is not always feasible. We examine the clinical outcomes of the NeoChord procedure after failed conventional mitral valve repair. A total of 312 patients were treated with the NeoChord repair procedure between January 2014 and December 2018 at 5 European centers. Clinical and echocardiographic data were reviewed to identify patients who had a prior surgical mitral valve repair procedure. The primary endpoint (Patient Success) was a composite of placement of at least 2 neochordae and end-procedure mitral valve regurgitation (MR) ≤ mild, freedom from death, stroke, structural or func…

Reoperation and the centrifugal pump?

1992

Postperfusion syndrome is still a problem in long cardiac operations using extracorporeal circulation (ECC). To evaluate whether or not centrifugal blood pumping during open heart surgery is beneficial, a randomized, prospective study was undertaken of 50 consecutive patients undergoing elective coronary artery bypass grafting. The patients were divided into two groups of 25 each. In group 1 a centrifugal pump (Biomedicus) was used as arterial blood pump, while in group 2 a roller pump (Stockert) was used. The two groups did not differ significantly and the number of variables during surgery was kept low (identical perfusion set, two surgeons, minimal cardiotomy suction). The parameters stu…