Artículos de publicaciones periódicas
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Browsing Artículos de publicaciones periódicas by Subject "DISPERSION RAMAN"
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artículo de publicación periódica.listelement.badge Anti-stokes Raman gain enabled by modulation instability in mid-IR waveguides(2018-11) Sánchez, Alfredo D.; Fierens, Pablo Ignacio; Hernández, Santiago M.; Bonetti, Juan I.; Brambilla, Gilberto; Grosz, Diego"The inclusion of self-steepening in the linear stability analysis of modulation instability (MI) leads to a power cutoff above which the MI gain vanishes. Under these conditions, MI in mid-IR waveguides is shown to give rise to the usual double-sideband spectrum but with Raman-shaped sidelobes. This results from the energy transfer of a CW laser simultaneously to both stokes and anti-stokes bands in pseudo-parametric fashion. As such, the anti-stokes gain matches completely the stokes profile over the entire gain bandwidth. This remarkable behavior, not expected from an unexcited medium, is shown not to follow from a conventional four-wave mixing interaction between the pump and the Stokes band. We believe this observation to be of relevance in the area of Raman-based sensors, which, in several instances, rely on monitoring small power variations of the anti-stokes spectral component."artículo de publicación periódica.listelement.badge A higher-order perturbation analysis of the nonlinear Schrödinger equation(2019-06) Bonetti, Juan I.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Grosz, Diego"A well-known and thoroughly studied phenomenon in nonlinear wave propagation is that of modulation instability (MI). MI is usually approached as a perturbation to a pump, and its analysis is based on preserving only terms which are linear on the perturbation, discarding those of higher order. In this sense, the linear MI analysis is relevant to the understanding of the onset of many other nonlinear phenomena, such as supercontinuum generation, but it has limitations as it can only be applied to the propagation of the perturbation over short distances. In this work, we propose approximations to the propagation of a perturbation, consisting of additive white noise, that go beyond the linear modulation instability analysis, and show them to be in excellent agreement with numerical simulations and experimental measurements."artículo de publicación periódica.listelement.badge Photon-conserving generalized nonlinear Schrödinger equation for frequency-dependent nonlinearities(2020) Bonetti, Juan I.; Linale, N.; Sánchez, Alfredo D.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Grosz, Diego"Pulse propagation in nonlinear waveguides is most frequently modeled by resorting to the generalized nonlinear Schrödinger equation (GNLSE). In recent times, exciting new materials with peculiar nonlinear properties, such as negative nonlinear coefficients and a zero-nonlinearity wavelength, have been demonstrated. Unfortunately, the GNLSE may lead to unphysical results in these cases since, in general, it does not preserve the number of photons and, in the presence of a negative nonlinearity, predicts a blue shift due to Raman scattering. In this paper, we put forth a modified GNLSE that can be used to model the propagation in media with an arbitrary, even negative, nonlinear coefficient. This novel photon-conserving GNLSE (pcGNLSE) ensures preservation of the photon number and can be solved by the same tried and trusted numerical algorithms used for the standard GNLSE. Finally, we compare results for soliton dynamics in fibers with different nonlinear coefficients obtained with the pcGNLSE and the GNLSE."artículo de publicación periódica.listelement.badge Simple method for estimating the fractional Raman contribution(2019-02) Sánchez, Alfredo D.; Linale, N.; Bonetti, Juan I.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Brambilla, Gilberto; Grosz, Diego"We propose a novel and simple method for estimating the fractional Raman contribution, fR, based on an analysis of a full model of modulation instability (MI) in waveguides. An analytical expression relating fR to the MI peak gain beyond the cutoff power is explicitly derived, allowing for an accurate estimation of fR from a single measurement of the Raman gain spectrum."artículo de publicación periódica.listelement.badge Tunable Raman gain in mid-IR waveguides(2018) Sánchez, Alfredo D.; Hernández, Santiago M.; Bonetti, Juan I.; Fierens, Pablo Ignacio; Grosz, Diego"By means of theoretical analysis and numerical simulations, we show a tunable Raman gain which may find applications in a variety of fields, ranging from mid-IR fiber Raman lasers and supercontinuum generation to ultra-wideband slow-light Raman-based devices. In particular, by analyzing the interplay among Raman gain, dispersion, and self-steeping (SE) in a full model of modulation instability (MI) in waveguides, we show that there exists a range of pump powers where the gain spectrum is not only dominated by the Raman contribution, but also, most strikingly, it can be fine-tuned at will. We present analytical and numerical results, in excellent agreement, confirming this observation. "