Quartic solitons of a mode-locked laser distributed model

Dissipative quartic solitons have gained interest in the field of mode-locked lasers for their energy-width scaling which, if identical to the one found in conservative quartic solitons, would allow the generation of ultrashort pulses with high energies. Pursuing the characterization of such solitons, here we found soliton solutions of a distributed model for mode-locked lasers in the presence of group velocity and fourth order dispersions (GVD and 4OD respectively), for two saturable absorber saturation powers. We found that the energy of the pulses follows an inverse relation with the width, with most cases following a different trend than the one found for conservative quartic solitons. Nevertheless, for higher saturation powers and negative 4OD, the pulses showed a behaviour approximate to the one found in the conservative regime, and were the most energetic and the shortest

Analysis of the coupling between a single-mode fiber to a multi-core fiber with long-period gratings

In this paper, the coupling of a single source injected in a single-mode fiber to all the cores of a multi-core fiber is theoretically studied. The power transfer between the core and the cladding of a fiber is promoted by long-period gratings. To promote the power transfer between the fibers, we considered cladding modes with similar effective refractive index. The results show that the coupling is possible, but the design still needs to be optimized to maximize the power transfer.publishe

Simulação de um sensor ótico baseado em microcavidade ressonante para medição de índice de refração

Neste trabalho, foi desenvolvido um algoritmo para simular a propagação do campo eletromagnético num tubo capilar quando acoplado com uma microfibra ótica, com recurso à teoria de dispersão de Mie, determinando os seus modos ressonantes. A utilização de um tubo capilar permite não só o acoplamento de luz, como também a circulação de fluidos no seu interior, apresentando vantagens como elemento sensor. Devido às suas reduzidas dimensões, com diâmetro interno de 96 um, serão necessários pequenos volumes de analito para provocar alterações no comprimento de onda de ressonância. Além disso, este tipo de microcavidades apresenta fatores de qualidade muito elevados, o que permite obter sensores com elevada resolução. As simulações efetuadas consideraram a propagação de modos com diferentes ordens angulares e radiais e tubos capilares com diferentes espessuras. Observou-se que quanto menor a espessura, maior será o campo evanescente no interior do tubo capilar, o que leva a uma maior interação luz-fluido. Considerando fluidos com índices de refração a variar entre 1.33 e 1.40, os quais representam misturas de água e glucose ou água e frutose (açúcares tipicamente encontrados no vinho da Madeira), verificou-se uma sensibilidade não linear (Fig. 1). Assim, consideraram-se dois intervalos distintos, para índices de refração baixos (1,33 – 1,36) e índices de refração altos (1,36 – 1,40). Para o primeiro intervalo, obteve-se uma sensibilidade máxima de 524,21 nm/UIR (unidade de índice de refração) enquanto para o segundo esta foi de 702,47 nm/UIR, para um modo com polarização TE, ordem radial n = 3 e capilar com espessura de 2,5 um.in publicatio

Analysis of long period gratings inscribed by CO2 laser irradiation and estimation of the refractive index modulation

Long period gratings (LPGs) inscribed in single mode fibers (SMFs) using CO2 laser irradiation were modelled numerically using the coupled mode method. The model considers the specifications of the inscription technique, such as the shape of the refractive index modulation that mimics the circularly symmetric point-to-point laser irradiation profile. A simple expression for predicting the resonant wavelength was obtained assuming a two-mode coupling model. However, to explain the spectra of the experimental LPGs, it was necessary to assume a reasonably high refractive index change and a multimode coupling model. Furthermore, using the developed model and a genetic algorithm to fit experimental resonances to simulated ones, we were able to estimate the maximum refractive index change, obtaining a value of 2.2 × 10-3, confirming the high refractive index change. The proposed model also predicts a second order resonance for this high value of refractive index change that was confirmed experimentally. Hence, with this model, we found some significant differences in the LPGs behavior when compared with conventional ones, namely, the emergence of coupling between different cladding modes and the competition of first and second order resonances which change the LPG transmission spectrum.publishe

Existence and stability of of multihumped femtosecond solitons

The propagation of bound soliton pairs in nonlinear photonic crystal fibers has recently been experimentallyobserved. The system may be modeled by a generalized nonlinear Schrödinger equation (GNLSE) whichincludes higher intrapulse Raman Scattering, self-steepening and higher order dispersion. Here, we findmultihumped pulses as result of an accelerating similarity reduction of a GNLSE containing the intrapulseRaman scattering. Numerical simulations of the suitable GNLSE using these solutions as input showed that theyare not stable, however, they may be related with the experimentally observed bound pairs since they propagatesteadily for distances compared to the ones observed

Optical and digital key enabling techniques for SDM-based optical networks

In order to support, in a cost-effective way, the data capacity demand in the context of future 5G networks, a new set of advanced technologies need to be explored, as it is the case of space-division multiplexing (SDM) along with energy efficient coherent detection based modulation formats. This paper presents the recent results on enabled optical networks based on SDM for high capacity optical networks compatible with 5G network infrastructure and data center connectivity. In particular, we demonstrate the viability of using Long-Period Gratings (LPGs) in multicore fibers (MCFs) to develop different components for multicore-based SDM systems, such as pump couplers and core/wavelength selective multi-core switches and couplers. Moreover, we also present and characterize the performance of different digital signal processing (DSP) algorithms and subsystems supporting optical coherent detection in SDM systems.publishe

Cole-Hopf Like Transformation for Schr\"odinger Equations Containing Complex Nonlinearities

We consider systems, which conserve the particle number and are described by Schr\"odinger equations containing complex nonlinearities. In the case of canonical systems, we study their main symmetries and conservation laws. We introduce a Cole-Hopf like transformation both for canonical and noncanonical systems, which changes the evolution equation into another one containing purely real nonlinearities, and reduces the continuity equation to the standard form of the linear theory. This approach allows us to treat, in a unifying scheme, a wide variety of canonical and noncanonical nonlinear systems, some of them already known in the literature. pacs{PACS number(s): 02.30.Jr, 03.50.-z, 03.65.-w, 05.45.-a, 11.30.Na, 11.40.DwComment: 26 pages, no figures, to be appear in J. Phys. A: Math. Gen. (2002

Halting the fuse discharge propagation using optical fiber microwires

We report and analyze the halting of the fuse effect propagation in optical fiber microwires. The increase of the mode field diameter in the tapered region decreases the optical intensity resulting in the extinction of the fuse effect. This fiber element presents a low insertion loss and can be introduced in the optical network in order to protect the active equipment from the damage caused by the fuse effect

Core Switch Using Optically Induced Long-Period Gratings

We propose and theoretically demonstrate an optically induced long-period gratings (OLPGs) based core switching technique for multi-core fibers (MCFs). This switching technique is fully reconfigurable in terms of signal wavelength and input–output fiber cores. The switching window and its efficiency can be adjusted by changing the peak power and the shape of the pump pulses, respectively. Switching efficiencies of 76% were found. Furthermore, we also show that the switched signal can be reshaped by tuning the shape of the pump pulses