Fast and slow light in zig-zag microring resonator chains

We analyze fast and slow light transmission in a zig-zag microring resonator chain. This novel device permits the operation in both regimes. In the superluminal case, a new ubiquitous light transmission effect is found whereby the input optical pulse is reproduced in an almost simultaneous manner at the various system outputs. When the input carrier is tuned to a different frequency, the system permits to slow down the propagating optical signal. Between these two extreme cases, the relative delay can be tuned within a broad range

Waves, analytical signals, and some postulates of quantum theory

In this paper we apply the formalism of the analytical signal theory to the Schrödinger wavefunction. Making use exclusively of the wave-particle duality and the rinciple of relativistic covariance, we actually derive the form of the quantum energy and momentum operators for a single nonrelativistic particle. Without using any more quantum postulates, and employing the formalism of the characteristic function, we also derive the quantum-mechanical prescription for the measurement probability in such cases

Properties of light resonances from unitarized Chiral perturbation theory: Nc behavior and quark mass dependence

We review the unitarization of Chiral Perturbation Theory with dispersion relations and how it describes meson-meson scattering data, generating light resonances whose mass, width and nature can be related to QCD parameters like quark masses and the number of colors.Comment: Invited review talk for the New Frontiers in QCD 2010, Yukawa International Program for Quark-Hadron Sciences (YIPQS), January 18 (Mon) - March 19 (Fri), 2010 Yukawa Institute for Theoretical Physics, Kyoto, Japan. To appear in Progress of Theoretical Physic

Characterization of a FBG sensor interrogation system based on a mode-locked laser scheme

"© 2017 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"[EN] This paper is focused on the characterization of a fiber Bragg grating (FBG) sensor interrogation system based on a fiber ring laser with a semiconductor optical amplifier as the gain medium, and an in-loop electro-optical modulator. This system operates as a switchable active (pulsed) mode-locked laser. The operation principle of the system is explained theoretically and validated experimentally. The ability of the system to interrogate an array of different FBGs in wavelength and spatial domain is demonstrated. Simultaneously, the influence of several important parameters on the performance of the interrogation technique has been investigated. Specifically, the effects of the bandwidth and the reflectivity of the FBGs, the SOA gain, and the depth of the intensity modulation have been addressed. (C) 2017 Optical Society of AmericaThis work has been partially supported by the Spanish MINECO through project TEC2014-60378-C2-1-R MEMES; the Generalitat Valenciana (APOSTD/2016/015), Sistema Nacional de Garantia Juvenil grant PEJ-2014-A-75865 (Promocion de Empleo Joven e Implantacion de la Garantia Juvenil 2014, MINECO); the Galician Regional Government under project GRC2015/018; the support of FINESSE the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska - Curie Action grant agreement no 722509; the National Natural Science Foundation of China (61405166) and the China Scholarship Council.Madrigal-Madrigal, J.; Fraile-Pelaez, FJ.; Zheng, D.; Barrera Vilar, D.; Sales Maicas, S. (2017). Characterization of a FBG sensor interrogation system based on a mode-locked laser scheme. Optics Express. 25(20):24650-24657. https://doi.org/10.1364/OE.25.024650S24650246572520Kersey, A. D., Davis, M. A., Patrick, H. J., LeBlanc, M., Koo, K. P., Askins, C. G., … Friebele, E. J. (1997). Fiber grating sensors. Journal of Lightwave Technology, 15(8), 1442-1463. doi:10.1109/50.618377Kersey, A. D., & Morey, W. W. (1993). Multiplexed Bragg grating fibre-laser strain-sensor system with mode-locked interrogation. Electronics Letters, 29(1), 112-114. doi:10.1049/el:19930073Chen, D., Shu, C., & He, S. (2008). Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser. Optics Letters, 33(13), 1395. doi:10.1364/ol.33.001395Huber, R., Wojtkowski, M., & Fujimoto, J. G. (2006). Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography. Optics Express, 14(8), 3225. doi:10.1364/oe.14.003225Ahmad, H., Ooi, H. C., Sulaiman, A. H., Thambiratnam, K., Zulkifli, M. Z., & Harun, S. W. (2008). SOA based fiber ring laser with Fiber Bragg Grating. Microwave and Optical Technology Letters, 50(12), 3101-3103. doi:10.1002/mop.23895Ooi, H. C., Ahmad, H., Sulaiman, A. H., Thambiratnam, K., & Harun, S. W. (2008). High-power single-wavelength SOA-based fiber-ring laser with an optical modulator. Laser Physics, 18(11), 1349-1352. doi:10.1134/s1054660x08110261Cole, M. J., Laming, R. I., Barcelos, S., Loh, W. H., & Zervas, M. N. (1995). Moving fibre/phase mask-scanning beam technique for enhanced flexibility in producing fibre gratings with uniform phase mask. Electronics Letters, 31(17), 1488-1490. doi:10.1049/el:1995098

Characterization of microring filters for differential group delay applications

The longitudinal offset technique permits to improve the accuracy of the coupling coefficients of integrated directional couplers and provides designs that can be easily implemented with current fabrication tolerances. In this work, we address the additional degree of freedom offered by this technology in order to tailor the differential group delay in coupled-resonator optical filters. We present the characterization of several devices exploiting this feature and we discuss their potential applicationsThis work has been founded by MINECO (Spanish Government), project numbers TEC2010-21303-C01, 02, 03 and 04, and JCyL Project No. VA089U16. F. J. F.-P. has also been partly supported by the ERDF and by the Galician Regional Government under project GRC2015/018 and under agreement for funding AtlantTI

Chiral Symmetry and light resonances in hot and dense matter

We present a study of the $\pi\pi$ scattering amplitude in the $\sigma$ and $\rho$ channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards chiral symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering amplitudes, (b) by finite nuclear density effects associated to a renormalization of the pion decay constant, and complementarily (c) by extending our calculation of the scalar-isoscalar channel to account for finite nuclear density and temperature effects in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological aspects relevant for nuclear matter and Heavy-Ion Collision experiments, such as $\rho$ mass scaling vs broadening from dilepton spectra and chiral restoration signals in the $\sigma$ channel. We also elaborate on the molecular nature of $\pi\pi$ resonances.Comment: 14 pages, 14 figures. Contribution to Hard Probes 2008, Illa de A Toxa, Spain, June 8th-14th 200

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks