Design of Single-Mode Single-Polarization Large-Mode-Area Multicore Fibers.

In laser science and industry, considerable effort is directed toward designing fibers for fiber laser and fiber amplifier applications, each of which offers a particular advantage over the others. Evanescently coupled multicore fibers, however, have been studied less extensively due to the relatively small mode area in the single-mode regime. Here, by proposing a new structure with stress-applying parts in a 37-core fiber and optimizing this structure through a comprehensive framework, we present 21 solutions characterized by large-mode-area and high beam quality in the single-mode, single-polarization regime. Different fiber designs are optimal for different output parameters. In one design, the mode area can significantly increase to above 880 µm2, which is comparable with that of photonic-crystal fibers. Moreover, besides the single-mode operation, the beam quality factor (M2 factor) of the fundamental mode is considered an output parameter in the bent state and is improved up to 1.05 in another design. A comprehensive tolerance analysis is then performed to assess the performance of the designs under deviations from normal conditions. Moreover, in spite of the shifts in the loss of modes, the proposed high beam quality LMA fibers maintain single-polarization, single-mode operation across a wide range of core pitches, bending orientation angles, and bending radius deviations. Our results highlight the potential of multicore fibers for the efficient operation of fiber lasers and amplifiers.

LED-pumped Cr:LiSAF laser system operating at 100†Hz based on a multipass amplifier.

The LED-pumping technology is used for the first time, to the best of our knowledge, to develop a complete master oscillator power amplifier (MOPA) system including a multipass amplifier. A pumping head using an original slab architecture is developed integrating a Cr:LiSAF slab pumped by 2112 blue LEDs via a Ce:YAG luminescent concentrator. The slab configuration enables the reaching of a large number of passes-up to 22-together with access to efficient cooling, allowing for a repetition rate scale up. For 22 passes, the amplifier delivers pulses with energy up to 2.4 mJ at 10-Hz repetition rate with a gain of 4.36 at 825 nm. A complete study of the MOPA is described, concluding in nearly constant performances versus the repetition rate, up to 100 Hz.

Postprocedural Radial Artery Compression Time In Chronic AnticoaguLated patients using StatSeal: The PRACTICAL-SEAL study.

BACKGROUND: Patients on uniterrupted chronic oral anticoagulation (OAC) therapy are at high-risk of bleeding during cardiac catheterization. We aimed to investigate the safety and efficacy of the StatSeal® disc for adjunct hemostasis in patients undergoing transradial coronary angiography under uninterrupted OAC therapy. METHODS: Patients who underwent transradial cardiac catheterization without interrupted OAC therapy were included in this study. RESULTS: Among 180 patients, 85 (47.2%) patients were on warfarin and 95 (52.8%) patients on novel oral anticoagulants (NOACs). Patients on NOACs were older (72.9 ± 9.6 versus 69.7 ± 10.8 years, P < 0.001) and had more atrial fibrillation/flutter (94.7% versus 62.4%, P < 0.001), whereas patients on Warfarin were more often women (43.5% versus 26.3%, P = 0.02) and had mechanical heart valves (27.1% versus 0%, P < 0.001). Intravenous unfractioned heparin (UFH) was administered in 96.5% of patients on warfarin (3799 ± 1342 units) and 93.7% patients on NOACs (4028 ± 1362 units), P = 0.27. There were no differences in terms of type and sheath size and the need for ad hoc coronary intervention. Time-to-first release of the hemostatic wristband was 56.2 ± 12.6 min and complete hemostasis was achieved in 71.1 ± 13.0 min, with shorter times among patients on NOACs (54.1 ± 11.7 and 58.5 ± 13.2 min, 68.9 ± 11.7 versus 73.6 ± 14.0 min, P = 0.02, for both). There were no significant differences in terms of bleeding. There was no radial artery occlusion among 112 participants who underwent color Doppler ultrasound. CONCLUSION: The present study shows that in patients undergoing transradial coronary angiogram under contemporary uninterrupted OAC therapy and periprocedural administration of UFH, the use of StatSeal® disc for adjunctive hemostasis was associated with short times to complete hemostasis.

LED-pumped femtosecond Cr:LiSAF regenerative amplifier system.

We report on the first, to the best of our knowledge, LED-pumped femtosecond regenerative amplifier. It is based on a Cr:LiSAF crystal pumped by 2240 blue LEDs via a Ce:YAG luminescent concentrator. The amplifier was seeded by pulses from a Ti:sapphire oscillator at 835 nm temporally stretched from 90 fs to 100 ps. At the output of the regenerative amplifier, we obtain 1 mJ pulse energy at a 10 Hz repetition rate, given by the frequency of the LED-pumping module. After compression, we obtain 100 fs pulses with a spectral bandwidth of 10 nm at 835 nm.

First Candida auris Outbreak during a COVID-19 Pandemic in a Tertiary-Care Center in Lebanon.

Candida auris is an emerging fungal pathogen considered as a global health threat. Recently there has been growing concern regarding drug resistance, difficulty in identification, as well as problems with eradication. Although outbreaks have been reported throughout the globe including from several Arab countries, there were no previous reports from Lebanon. We herein report the first cases of C. auris infection from the American University of Beirut Medical Center, a tertiary care center in Lebanon describing the clinical features of the affected patients in addition to the infection control investigation and applied interventions to control the outbreak. Fourteen patients with C. auris infection/colonization identified using MALDI-TOF and VITEK 2- Compact system were reported over a period of 13 weeks. Patients were admitted to four separate critical care units. All of them came through the emergency room and had comorbid conditions. Half of the patients were infected with COVID-19 prior to isolation of the C. auris. C. auris was isolated from blood (two isolates), urine (three isolates), respiratory tract (10 isolates) and skin (one isolate). All the patients had received broad spectrum antibiotics prior to isolation of C. auris. Six patients received antifungal treatment, while the remaining eight patients were considered colonized. Environmental cultures were taken from all four units and failed to isolate the organism from any cultured surfaces. A series of interventions were initiated by the Infection Prevention and Control team to contain the outbreak. Rapid detection and reporting of cases are essential to prevent further hospital transmission. A national standardized infection control registry needs to be established to identify widespread colonization.

Short Durations of Radial Hemostatic Device After Diagnostic Transradial Cardiac Catheterization: The PRACTICAL-2 Randomized Trial.

BACKGROUND: Radial artery occlusion (RAO) is the most common complication following transradial approach (TRA) for cardiac catheterisation. Our aim was to assess if decreasing radial hemostatic device (RHD) time reduces the risk of RAO among individuals receiving small sheath sizes with no adjunctive heparin. METHODS: We randomised 450 individuals undergoing diagnostic cardiac catheterization via TRA to 3 durations of RHD time: 10, 20, or 30 minutes. After these time periods, the RHD was gradually released over 20 minutes. The primary efficacy end point was forearm hematoma grade ≥ 2 (5-10 cm) and the primary safety end point was RAO (as determined by Doppler ultrasound) 1 hour after RHD removal (before discharge). RESULTS: The mean age was 66 years and 64% were male. Five-French sheaths were used in all patients. Hematoma grade ≥ 2 occurred in only 1 patient, who was in the 20-minute group (P = 0.39). RAO occurred in 6.7% of patients in the 10-minute group, 10.7% in the 20-minute group and 6% in the 30-minute group (P = 0.26). CONCLUSIONS: Among patients receiving small-caliber sheaths without adjunctive heparin, the incidence of forearm hematoma and RAO are low. Shorter durations of RHD time did not further reduce the risk of these complications.

Design optimization of orbital angular momentum fibers using the gray wolf optimizer.

Optical data communication based on the orbital angular momentum (OAM) of light is a recently proposed method to enhance the transmission capacity of optical fibers. This requires a new type of optical fiber, the main part of the optical communication system, to be designed. Typically, these fibers have a ring-shaped refractive index profile. We aim to find an optimized cross section refractive index profile for an OAM fiber in which the number of supported OAM modes (channels), mode purity, and the effective refractive index separation of OAM modes to other fibers modes are maximized. However, the complexity of the relationship between structural parameters and optical transmission properties of these fibers has resulted in the lack of a comprehensive analytical method to design them. In this paper, we investigate the process of designing OAM fibers and propose a framework to design such fibers by using artificial intelligence optimizers. It is worth mentioning here that this problem is intrinsically a multiobjective optimization problem, and the actual solution for such problems is not unique and leads to a set of optimum solutions. Therefore, at the end of the optimization process, a wide range of optimal designs will be obtained in which a trade-off is established in each of the solutions. We solve this problem with the multiobjective gray wolf optimizer (GWO) and compare the results with that of the single-objective GWO. The framework can easily find many optimal designs that support more than 20 OAM modes. The obtained results show that the proposed method is comprehensive and can optimize the structure of any OAM fibers. No human involvement, simplicity, and being straightforward are the main advantages of the proposed framework.

Tunable UV source based on an LED-pumped cavity-dumped Cr:LiSAF laser.

We developed a light-emitting diode (LED)-pumped Cr:LiSAF laser operating in Q-switched and cavity-dumped regimes. The laser produces 1.1 mJ pulses with a pulse duration of 8.5 ns at a repetition rate of 10 Hz on a broad spectrum centered at 840 nm with a full width at half maximum of 23 nm. After frequency tripling in two cascaded LBO crystals, we obtained 7 ns pulses with an energy of 13 µJ at 280 nm and with a spectral width of 0.5 nm, limited by the spectral acceptance of the phase matching process. By rotating both LBO crystals, UV emission is tuned from 276 nm to 284 nm taking advantage of the broad infrared spectrum of the Cr:LiSAF laser.

Designing a low-threshold quantum-dot laser based on a slow-light photonic crystal waveguide.

We numerically investigate and design a compact electrically pumped edge-emitting photonic crystal waveguide (PCW) quantum dot (QD) laser operating at room temperature. Use of a narrowband folded directional coupler as the output mirror has made the proposed structure an edge-emitting single-mode laser. Moreover, we propose a set of rate equations to model the performance of the PCW-QD laser. In the proposed model, we take the effects of the homogeneous and inhomogeneous broadenings and the slow-light effects on the modal gain and loss coefficient into account. Simulations show that threshold current as low as ∼26 µA can be achieved for the PCW-QD laser with a 50-µm-long cavity and output power in the range of micro-watts. The proposed low-threshold edge-emitting PCW-QD laser is a promising light source for the off-chip and on-chip photonic network applications.

Design of a low-power all-optical NOR gate using photonic crystal quantum-dot semiconductor optical amplifiers.

Design and simulation of a novel all-optical logic gate (AOLG) based on photonic crystal quantum-dot semiconductor optical amplifiers (PC-QDSOAs) is reported for the first time. For this purpose, a flat-band slow-light QD-based active photonic crystal waveguide (APCW) is designed and employed for implementation of an all-optical NOR gate in a symmetric Mach-Zehnder interferometer configuration. Then, the performance of the NOR gate is investigated using a comprehensive nonlinear state space model (NSSM). Simulation results demonstrate that PC-QDSOAs present an interesting platform for realizing ultracompact AOLGs with low power consumption.

Operation of quantum-dot semiconductor optical amplifiers under nonuniform current injection.

The influence of nonuniform current injection along the active region, on the linear operation of a quantum-dot semiconductor optical amplifier (QD-SOA) is investigated. For this purpose, we have utilized some functions to generate various nonuniform current injection profiles. These profiles have been considered in our numerical calculations, where the rate equation model is employed to construct different characteristics of the QD-SOA. We have found that the gain, as well as the crosstalk, of a QD-SOA is closely associated to the variance of the carrier density along the cavity. Simulation results show that nonuniform current injection can be used as a technique for gain enhancement as well as crosstalk suppression.