ABSTRACT
We put forth a theoretical model allowing for the analysis of short-pulse interactions at time boundaries in waveguides with arbitrary frequency-dependent nonlinear profiles, in particular those exhibiting a zero-nonlinearity wavelength. Moreover, this is performed within a photon-conserving framework, thus circumventing use of the nonlinear Schrödinger equation in such scenarios, as it may lead to unphysical outcomes. Results indicate that the waveguide zero-nonlinearity wavelength has a great influence on said interactions, specifically by defining spectral bands where either signal total reflection or signal transmission can occur. We believe these findings to be of relevance in the area of all-optical switching schemes based on the interaction of short pulses in nonlinear media.
ABSTRACT
We propose an original, simple, and direct method to measure self-steepening (SS) in nonlinear waveguides. Our proposal is based on results derived from the recently introduced photon-conserving nonlinear Schrödinger equation (NLSE) and relies on the time shift experienced by soliton-like pulses due to SS upon propagation. In particular, a direct measurement of this time shift allows for a precise estimation of the SS parameter. Furthermore, we show that such an approach cannot be tackled by resorting to the NLSE. The proposed method is validated through numerical simulations, in excellent agreement with the analytical model, and results are presented for relevant spectral regions in the near infrared, the telecommunication band, and the mid infrared, and for realistic parameters of available laser sources and waveguides. Finally, we demonstrate the robustness of the proposed scheme against deviations expected in real-life experimental conditions, such as pulse shape, pulse peak power, pulsewidth, and/or higher-order linear and nonlinear dispersion.
ABSTRACT
We exploit the anisotropic plasmonic behavior of gold nanorods (AuNRs) to obtain a waveguide with a nonlinear coefficient dependent on both the frequency and polarization of incident light. The optical properties of the waveguide are described by an extension of the Maxwell Garnett model to nonlinear optics and anisotropic nanoparticles. Then, we perform a study of modulation instability (MI) in this system by resorting to the recently introduced photon-conserving nonlinear Schrödinger equation (pcNLSE), as the pcNLSE allows us to model propagation in nonlinear waveguides of arbitrary sign and frequency dependence of the nonlinear coefficient. Results show that the anisotropy of the nanorods leads to two well-differentiated MI regimes, a feature that may find applications in all-optical devices.
ABSTRACT
In this Letter, we present, for the first time, to the best of our knowledge, the modulation instability (MI) gain spectrum of waveguides with an arbitrary frequency-dependent nonlinear coefficient ensuring strict energy and photon-number conservation of the parametric process. This is achieved by starting from a linear stability analysis of the recently introduced photon-conserving nonlinear Schrödinger equation. The derived MI gain is shown to predict some unique features, such as a nonzero gain extending beyond a zero-nonlinearity wavelength and a complex structure of the MI gain spectrum. Analytical results are shown to be in excellent agreement with numerical simulations.
ABSTRACT
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.
