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A new class of partially coherent model sources is introduced on the basis of the second-order coherence theory of nonstationary optical fields. These model sources are spatially fully coherent at each frequency but can have broadband spectra and variable spectral coherence properties, which lead to reduced spatiotemporal coherence in the time domain. The source model is motivated by the spectral coherence properties of supercontinuum pulse trains generated in single-spatial-mode optical fibers. We demonstrate that such broadband light is highly (but not completely) spatially coherent, even though the spectral and temporal coherence properties may vary over a wide range. The model sources introduced here are convenient in assessing the spatiotemporal coherence of broadband pulses in optical systems.

We report control of the spectral and noise properties of spontaneous modulation instability (MI) in optical fiber using an incoherent seed with power at the 10(-6) level relative to the pump. We sweep the seed wavelength across the MI gain band, and observe significant enhancement of MI bandwidth and improvement in the signal-to-noise ratio as the seed coincides with the MI gain peak. We also vary the seed bandwidth and find a reduced effect on the MI spectrum as the seed coherence decreases. Stochastic nonlinear Schrödinger equation simulations of spectral and noise properties are in excellent agreement with experiment.

The transient appearance of bright spots in the beam profile of optical filaments formed in xenon is experimentally investigated. Fluence profiles are recorded with high-speed optical cameras at the kilohertz repetition rate of the laser source. A statistical analysis reveals a thresholdlike appearance of heavy-tailed fluence distributions together with the transition from single to multiple filamentation. The multifilament scenario exhibits near-exponential probability density functions, with extreme events exceeding the significant wave height by more than a factor of 10. The extreme events are isolated in space and in time. The macroscopic origin of these experimentally observed heavy-tail statistics is shown to be local refractive index variations inside the nonlinear medium, induced by multiphoton absorption and subsequent plasma thermalization. Microscopically, mergers between filament strings appear to play a decisive role in the observed rogue wave statistics.

We demonstrate the concept of a merged nanoscale photonic crystal slot waveguide that acts as a bandpass filter in the near infrared region of the spectrum. The device is based on the integration of a photonic crystal cavity in a slot waveguide on a silicon on insulator substrate. The device is further embedded in amorphous titanium dioxide using atomic layer deposition, which allows to reduce two-photon absorption losses and creates the possibility to combine nonlinear guided-wave optics resulting from the strong field confinement in the slot region with slow light effects in the photonic crystal cavity. Our approach is fully compatible with complementary metal oxide semiconductor technology and opens up new perspectives for the integration of all-optical signal processing functionalities in hybrid silicon nanophotonics platforms.

Objective: To evaluate the additional value of StentBoost® (SB), a motion-corrected X-ray technique that enhances stent visualization, for the assessment of stent deployment and procedure optimization during routine percutaneous coronary interventions (PCI)., Background: Underdeployment and malapposition of stents during PCI may lead to in-stent thrombosis and restenosis. Coronary angiography (CA) is of limited value for the assessment of stent deployment. Intravascular ultrasound and optical imaging techniques are the gold standard, but are used in <10% of routine PCIs., Methods: We retrospectively analyzed 260 coronary lesions treated by stent implantation and assessed by SB during 168 consecutive PCI procedures. The immediate results of SB analysis and CA were assessed by 2 independent interventional cardiologists and compared., Results: A total of 275 stents were implanted; 45% were drug-eluting stents (DES). Direct stenting was performed in 78%. Results of SB and angiography were concordant for 210 lesions: 194 stents were correctly deployed (75%) and 16 were underdeployed (6%), shown by both techniques. In 47 patients (18%), SB detected an underdeployment of the stent whereas the angiographic result was good. Postdilatation was performed on the basis of SB in 89% of these cases. The additional contribution of SB was higher for left main lesions and for DES, and was not affected by coronary calcifications., Conclusions: This study confirmed the usefulness of the stent visualization enhancement technique StentBoost® in current PCI practice. SB revealed about 20% underdeployed stents not detected by CA, and allowed for optimizing PCI by ad hoc effective postdilatation., (© 2013, Wiley Periodicals, Inc.)

We use dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation. We study both the onset phase of supercontinuum generation with distinct dispersive wave generation, as well as a highly-unstable supercontinuum regime spanning an octave in bandwidth. Wavelength correlation maps allow interactions between separated spectral components to be identified, even when such interactions are not apparent in shot-to-shot or average measurements. Experimental results are interpreted using numerical simulations. Our results show the clear advantages of dispersive Fourier transformation for studying spectral noise during supercontinuum generation.

We present a supercontinuum (SC) light source designed for stroboscopic white light interferometry. The compact, cost-effective SC source is built from off-the-shelf optical components and operates both in the visible and near-IR at arbitrary repetition rates in the 10 kHz-1 MHz frequency range. We estimate that our source allows performing dynamic white-light interferometric characterization of rapidly oscillating objects up to several tens of megahertz. Its current potential is demonstrated by capturing the movement of a microelectromechanical system oscillating at 2.16 MHz with sub-100 nm accuracy.

We report on strong UV third-harmonic generation from silicon nitride films and resonant waveguide gratings. We determine the absolute value of third-order susceptibility of silicon nitride at wavelength of 1064 nm to be χ(³) (-3ω,ω,ω,ω) = (2.8 ± 0.6) × 10⁻²⁰m²/V², which is two orders of magnitude larger than that of fused silica. The third-harmonic generation is further enhanced by a factor of 2000 by fabricating a resonant waveguide grating onto a silicon nitride film. Our results extend the operating range of CMOS-compatible nonlinear materials to the UV spectral regime.

We report on a theoretical and experimental study of cascaded Bragg scattering in fiber optics. We show that the usual energy-momentum conservation of Bragg scattering can be considerably relaxed via cascade-induced phase-matching. Experimentally we demonstrate frequency translation over six- and 11-fold cascades, in excellent agreement with derived phase-matching conditions.

We describe a 17-year-old patient presenting perimyocarditis as the initial manifestation of the adult-onset Still's disease. Corticotherapy was rapidly successful but induced major acute hepatitis in relation with Epstein-Barr virus reactivation. After 1 year, even if the global outcome is favourable, a slightly lowered ejection fraction still persists. Former case reports and differential diagnosis with reactive haemophagocytic syndrome would be discussed.

We demonstrate a thousand-fold enhancement of second-harmonic generation in an all-dielectric silicon nitride (SiN) resonant waveguide grating compared to a flat SiN film. The strong second-harmonic output measured at 532 nm results from the combination of the enhanced local fields in the nanostructure and the large second-order susceptibility of SiN. The second-harmonic conversion efficiency in the resonant structure is found to be of the order of 10(-8), which is significantly larger than that typically observed from plasmonic metal nanostructures.

Aerosol techniques were used to synthesize spherical and monodisperse silver nanoparticles for plasmonic materials. The particles were generated with an evaporation-condensation technique followed by size selection and sintering with a differential mobility analyzer and a tube furnace, respectively. Finally, the nanoparticles were collected on a glass substrate with an electrostatic precipitator. The particle size distributions were measured with a scanning mobility particle sizer and verified with a transmission electron microscope. A spectrophotometer was used to measure the optical extinction spectra of the prepared samples, which contained particles with diameters of approximately 50, 90 and 130 nm. By controlling the particle size, the dipolar peak of the localized surface plasmon resonance was tuned between wavelengths of 398 and 448 nm. In addition, quadrupolar resonances were observed at shorter wavelengths as predicted by the simplified theoretical model used to characterize the measured spectra.

We apply the coherent-mode expansion to correlation functions used to describe the coherence properties of supercontinuum generated in nonlinear fibers. We show that the leading term of the expansion represents the quasi-coherent part of the field while the quasi-stationary part is embedded into the higher-order modes. The evolution of the modal expansion and the number of modes needed to describe the supercontinuum field are also discussed.

The ability to measure real-time fluctuations of ultrashort pulses propagating in optical fiber has provided significant insights into fundamental dynamical effects such as modulation instability and the formation of frequency-shifting rogue wave solitons. We report here a detailed study of real-time fluctuations across the full bandwidth of a fiber supercontinuum which directly reveals the significant variation in measured noise statistics across the spectrum, and which allows us to study correlations between widely separated spectral components. For two different propagation distances corresponding to the onset phase of spectral broadening and the fully-developed supercontinuum, we measure real time noise across the supercontinuum bandwidth, and we quantify the supercontinuum noise using statistical higher-order moments and a frequency-dependent intensity correlation map. We identify correlated spectral regions within the supercontinuum associated with simultaneous sideband generation, as well as signatures of pump depletion and soliton-like pump dynamics. Experimental results are in excellent agreement with simulations.

The nonlinear Schrödinger equation (NLSE) is a central model of nonlinear science, applying to hydrodynamics, plasma physics, molecular biology and optics. The NLSE admits only few elementary analytic solutions, but one in particular describing a localized soliton on a finite background is of intense current interest in the context of understanding the physics of extreme waves. However, although the first solution of this type was the Kuznetzov-Ma (KM) soliton derived in 1977, there have in fact been no quantitative experiments confirming its validity. We report here novel experiments in optical fibre that confirm the KM soliton theory, completing an important series of experiments that have now observed a complete family of soliton on background solutions to the NLSE. Our results also show that KM dynamics appear more universally than for the specific conditions originally considered, and can be interpreted as an analytic description of Fermi-Pasta-Ulam recurrence in NLSE propagation.

We report theoretical, numerical, and experimental studies of higher-order modulation instability in the focusing nonlinear Schrödinger equation. This higher-order instability arises from the nonlinear superposition of elementary instabilities, associated with initial single breather evolution followed by a regime of complex, yet deterministic, pulse splitting. We analytically describe the process using the Darboux transformation and compare with experiments in optical fiber. We show how a suitably low frequency modulation on a continuous wave field induces higher-order modulation instability splitting with the pulse characteristics at different phases of evolution related by a simple scaling relationship. We anticipate that similar processes are likely to be observed in many other systems including plasmas, Bose-Einstein condensates, and deep water waves., (© 2011 American Physical Society)

The authors report a case of acute type-B aortic dissection in association with an unknown isthmic coarctation in a 30-year-old adult. Successful surgical repair was performed 6 months later without cardiopulmonary bypass. Physiopathological aspects and surgical strategy are discussed. Acute aortic dissection distal to isthmic coarctation is extremely rare and has been reported in only 5 other cases. Present case is the first, to our knowledge, to be operated without cardiopulmonary bypass., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

We report on the experimental observation of nonlinear mixing between Raman-shifting solitons and residual pump radiation in supercontinuum generation in the long-pulse regime. This resonant coherent process results in the generation of strong and isolated spectral components on the long-wavelength normal dispersion regime of a fiber with two zero-dispersion wavelengths. Our observations are in excellent agreement with numerical simulations and calculated phase-matching conditions., (© 2011 Optical Society of America)

We introduce a concept to control the spectral and dichroic properties of metamaterials. The approach is based on anisotropic metal nanoparticles and on varying their mutual orientation in a periodic lattice. Even seemingly inconsequential changes in particle ordering strongly modify the dichroic properties of the arrays and result in either very narrow resonances or ultrabroad extinction ranges. The results arise from long-range diffractive coupling between the particles, as determined by the dependence of the array unit cell size on particle ordering.

We consider the accuracy of modeling ultrashort pulse propagation and supercontinuum generation in optical fibers based on the assumption of a material Raman response that varies linearly with frequency. Numerical simulations in silica fiber using the linear Raman gain approximation are compared with simulations using the full Raman response, and differences in the spectral, temporal and stability characteristics are considered. A major finding is that for conditions typical of many experiments, although the input pulses may satisfy the criteria where the linear gain approximation is valid, the subsequent evolution and breakup of the input pulse can rapidly lead to a situation where the linear model leads to severe inaccuracies. Numerical artifacts within the linear model inducing unphysical pulse collapse are also identified.

We analyze the coherence properties of supercontinuum generated in photonic crystal fibers by applying the second-order coherence theory of nonstationary light. Using an ensemble of simulated realizations, we construct two-frequency cross-spectral density and two-time mutual coherence functions. This allows us to introduce measures of temporal and spectral coherence. We show that, in the long-pulse regime, supercontinuum light can be decomposed into a sum of coherent and quasi-stationary contributions. Our approach and findings are also applicable in the short-pulse regime.

We report experimental evidence of dispersive waves with enhanced redshift generated through soliton collisions in a photonic crystal fiber with two zero-dispersion wavelengths. Experiments are performed to study both controlled collisions under twin-pulse excitation, as well as spontaneous collisions arising from noise-induced supercontinuum generation. Experimental results for the spectral and statistical properties are in good agreement with numerical simulations and are shown to be associated with extreme-value like distributions with long tails.

We study experimentally the statistical fluctuations observed in a supercontinuum generated in the normal dispersion regime through cascaded stimulated Raman scattering. Specifically, we show that the statistical distribution of shot-to-shot spectral variations evolves from a quasi-Gaussian in the saturated regime for Stokes orders near the pump to a long-tailed extreme-value distribution for Stokes orders at a large separation from the pump in the unsaturated regime.

Since its introduction as a routine arterial route for interventional cardiology, the radial route has been associated with higher X-rays doses, either to the patient and the operator. There is less evidence for this association in recent studies, probably due to the learning curve for this approach, improvement in radiological equipments and in radiation protection techniques. Coronary angiography and percutaneous coronary interventions can be performed by radial route routinely with very low levels of exposure for the patient (<50% of the reference levels). However, for a fixed dose to patient, the operator's exposure remains higher by radial route, compared to femoral route. Optimized individual radiation protection devices for operators are mandatory when procedures are performed by radial approach.

Background: Exposure of patients to radiation from invasive cardiac procedures is high and may be deleterious., Aims: To assess the effectiveness of a dose-reduction programme based on radiation-protection training, according to the recommendations of the Euratom Council, the International Commission on Radiological Protection and the French Society of Cardiology., Methods: In this single-centre survey, dose-area product (DAP, Gy.cm(2)), fluoroscopy time (minutes) and number of runs were evaluated in 3285 consecutive procedures (2077 coronary angiographies [CAs], 1208 percutaneous coronary interventions [PCIs]), performed one year before (2005) and two years after (2006 to 2007) implementation of a programme for radiation dose-reduction. The programme included a 2-day training course in radiological protection for all medical and paramedical staff and recommendations for routine use of low fluoroscopic and acquisition pulse rates (6.25 and 12.5 i/s, respectively), large field size (23cm), maximal collimation and optimal X-ray tube/patient/detector distances. Routine left ventriculography was discouraged. The radial approach was used in>80% of the procedures., Results: Compared with 2005, a significant 50% reduction in DAP was observed in 2006 and 2007 during CA (median [interquartile range] 53 Gy.cm(2) [33-84] vs 26 [16-43] and 21 [14-32], respectively; p<0.0001) and PCI (125 Gy.cm(2) [78-184] vs 49 [31-79] and 44 [27-66], respectively; p<0.0001). Fluoroscopy time and number of runs did not vary significantly in 2006, and decreased slightly in 2007, likely due to an important reduction in rate of left ventriculographies (from 32 to 4%). Inter-operator variability in DAP was reduced., Conclusion: Training in radiation protection for interventional cardiologists and use of simple and cost-free dose-reduction techniques were associated with a 50% reduction in radiation exposure to patients undergoing invasive cardiac procedures, without any loss of diagnostic information.

Numerical simulations are used to study the interaction dynamics between pump spectral broadening and third harmonic generation during supercontinuum generation in a highly nonlinear fused silica nanowire using sub-100 fs pump pulses. In particular, we show that the superposition of the generated third harmonic with the spectrally-broadened pump pulse exhibits significant dependence on the input pump carrier envelope phase, and we examine this dependence as a function of pulse duration and propagation distance.

We present a numerical study of the evolution dynamics of "optical rogue waves", statistically-rare extreme red-shifted soliton pulses arising from supercontinuum generation in photonic crystal fiber [D. R. Solli, et al. Nature 450, 1054-1058 (2007)]. Our specific aim is to use nonlinear Schrödinger equation simulations to identify ways in which the rogue wave dynamics can be actively controlled, and we demonstrate that rogue wave generation can be enhanced by an order of magnitude through a small modulation across the input pulse envelope and effectively suppressed through the use of a sliding frequency filter.

X-ray exposure of patient during coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA) may have some deleterious effects. The dose area product (DAP), related to the effective dose, is a measure of stochastic risk and a potential quality indicator. The aim of our study was to assess radiation exposure of patients in a large series of "real life" interventional cardiac procedures. We evaluated DAP and Fluoroscopy time (t) during CA and/or PTCA in 3600 consecutive patients from 2002 to 2005. Procedures were performed by five experienced physicians, using successively femoral and radial techniques. DAP and t significantly correlated (r = 0.73; p < 0.0001). Median [25th-75th percentiles] values for DAP and for t were 63 [40-101] Gy.cm2 and 6.3 [4-10] min for CA, 100 [62-178] Gy.cm2 and 14.0 [9-22] min for elective PTCA, and 141 [90-219] Gy.cm2 and 15.7 [11-23] min for CA immediately followed by ad hoc PTCA, respectively. Differences between operators ranged from 50% (CA) to 70% (PTCA) for both DAP and t (p < 0.001). Moving from the femoral to the radial approach resulted in a 1.5 to 2-fold increase in DAP in 2002 (p < 0.001). DAP and t then decreased toward the european DIMOND reference values (in 2005: 53.4 Gy.cm2 and 5.5 min for CA, 104.64 Gy.cm2 and 13.1 min for elective PTCA, 128.4 Gy.cm2 and 13.6 min for ad hoc PTCA). In conclusion, radiation exposure to patients and staff are strongly dependent on operators, time course, and the arterial access, due in part to the learning curve for radial approach. The enhanced knowledge of radiation dose is the first step of a radiation dose-reduction program, likely to minimize patient and operator radiation hazards in interventional cardiology. Definition of national reference values for DAP and fluoroscopy time would be helpful for appropriate comparisons.