Chalcogenide suspended-core fibers for supercontinuum generation in the mid-infrared

Chalcogenide suspended core fibers are a valuable solution to obtain supercontinuum generation of light in the mid-infrared, thanks to glass high transparency, high index contrast, small core diameter and widely-tunable dispersion. In this work the dispersion and nonlinear properties of several chalcogenide suspended core mi-crostructured fibers are numerically evaluated, and the effects of all the structural parameters are investigated. Optimization of the design is carried out to provide a fiber suitable for wide-band supercontinuum generation in the mid-infrared

Highly nonlinear chalcogenide suspended-core fibers for applications in the mid-infrared

Due to their unique dispersion and nonlinear properties, chalcogenide suspended-core fibers, characterized by a few micrometer-sized core suspended between large air-holes by few small glaß struts, are excellent candidates for mid-infrared applications. In the present study the influence of the main croß-section characteristics of the chalcogenide suspended-core fibers on the dispersion curve and on the position of the zero-dispersion wavelength has been thoroughly analyzed with a full-vector modal solver based on the finite element. In particular, the design of suspended-core fibers made of both As2S3 and As2Se3 has been optimized to obtain dispersion properties suitable for the supercontinuum generation in the mid-infrared

Inner cladding influence on large mode area photonic crystal fiber properties under severe heat load

International audienceThe influence of the size and the air-filling fraction of the inner microstructure on the first HOM confinement in Yb-doped LMA PCFs under different heat load values has been investigated with a full-vector modal solver based on the finite element method, used also to solve the steady-state heat equation. In particular, the air-cladding inner dimension and the air-hole diameter in Symmetry-Free PCFs and Large Pitch Fibers have been modified in order to study which conditions facilitate the coupling between HOM and cladding modes, thus improving the delocalization of the former and making the fiber single-mode behavior more robust

Analysis of the modal content into large-mode-area photonic crystal fibers under heat load

International audienceThanks to their capability to provide very large mode area together with effective suppression of high-order modes, while allowing strong pump absorption and efficient conversion, Yb-doped double-cladding photonic crystal fibers are one of the key enabling factors for the development of high power fiber lasers. Thermal effects are currently appointed as the main bottleneck for future power scaling since, beyond a certain average power, they allow guidance of high order modes and energy transfer to them, causing a sudden degradation of the beam quality. In this paper the effects of heat load on the modes of double cladding fibers are thoroughly analyzed with a full-vector modal solver based on the finite-element method with integrated steady-state heat equation solver. Fibers with different inner cladding designs are compared to provide a deeper understanding of the mechanisms beyond the mode reconfinement and coupling. The influence of the fiber design on the robustness of the single-mode regime with respect to fiber heating has been demonstrated, providing a clear picture of the complex interaction between modes. On the basis of simulation results it has been possible to group fiber modes into three families characterized by peculiar reaction to heating. Index Terms—Photonic crystal fibers, thermo-optic effect, fiber lasers and amplifiers

Large mode area aperiodic fiber designs for robust singlemode emission under high thermal load

International audienceIn this paper, we investigate the potential of various large mode area bers under thermal load, that is the state-of-the-art air-silica large pitch bers, as well as the recently devised symmetry-reduced photonic crystal ber and aperiodic all-solid by carefully considering the degrees of freedom oered all along the ber fabrication. This work aims to discuss the mode ltering ability of these structures in regard to the power scaling and to conrm their potential for robust singlemode operation at high power level. Structural principles contributing to improve their performances such as the impact of air holes / solid inclusions size will be presented. We also intend to establish that the range of average absorbed/output power for which a robust singlemode operation is available can be shifted to full user requests in term of power range

Hybrid Ytterbium-doped large-mode-area photonic crystal fiber amplifier for long wavelengths.

A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with build-in gain shaping is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes define the large-mode-area core. Light confinement is achieved by combined index and bandgap guiding, which allows for single-mode operation and gain shaping through distributed spectral filtering of amplified spontaneous emission. The fiber properties are ideal for amplification in the long wavelength regime of the Ytterbium gain spectrum above 1100 nm, and red shifting of the maximum gain to 1130 nm is demonstrated

Design of innovative photonic crystal fibers for high power lasers

Grazie alle loro eccellenti caratteristiche in termini di potenza in uscita, efficienza, compattezza e dissipazione termica, i laser in fibra stanno rapidamente sostituendo le altre sorgenti allo stato solido in molti ambiti di applicazione. Per consentire ulteriori progressi di questa tecnologia, sono necessarie fibre ottiche innovative, in grado di consentire stabilmente la propagazione in regime singolo modo in un core di grandi dimensioni. Le fibre a cristallo fotonico (Photonic Crystal Fiber - PCF) rappresentano la soluzione più conveniente, in virtù della loro proprietà di guidaggio ampiamente flessibili e della tecnologia di fabbricazione largamente affermata. Lo scopo di questa Tesi è di presentare i risultati riguardanti la progettazione di fibre a cristallo fotonico doppio cladding innovative, ottenuti nel corso di Dottorato presso il Dipartimento di Ingegneria dell'Informazione dell'Università di Parma. Dopo avere illustrato i principali problemi relativi all'aumento della potenza nei sistemi laser in fibra e le caratteristiche più importanti delle fibre a cristallo fotonico, vengono mostrati i risultati dell'analisi e ottimizzazione di diverse tipologie di PCF, ricavando linee guida per la progettazione di fibre attive per sorgenti di prossima generazione.Thanks to their superior properties in terms of output power, brightness, efficiency, compactness, and thermal management, fiber lasers are rapidly replacing other solid-state sources in many fields of application. In order to achieve further advancements of this technology, innovative active optical fibers are required, capable of allowing stable single-mode propagation in a large-area core. Photonic Crystal Fibers (PCFs) appear to be the most practical solution, thanks to their highly-tailorable guiding properties and well-established fabrication technology. The aim of this Thesis is to present the results on the design of innovative double cladding PCFs for high power fiber lasers, obtained during the Ph.D. course at the Information Engineering Department of the University of Parma. After a review of the most important issues related to power scaling of fiber laser systems and of the key features of photonic crystal fibers, the results of the analysis and optimization of different PCF designs are discussed, providing guidelines for the realization of active fibers for next-generation sources

Thermo-optical effects in large mode area photonic crystal fibers

High pulse energy and peak powers of fiber laser systems require the development of large effective area and new fiber designs. However thermally induced refractive index change is one major limitation to the achievable power, causing degradation of the modal properties and preventing to obtain stable diffraction-limited output beam. The effects of thermally induced refractive index change on the guiding properties of photonic crystal fibers are thoroughly investigated. © 2014 IEEE

Tm-doped rod-type photonic crystal fibers with symmetry-free cladding

A new design approach for large mode area Tm-doped photonic crystal fibers, based on the reduction of cladding symmetry, is numerically analyzed to demonstrate the possibility to obtain robust single-mode guiding under severe heat load