Laure Lavoute

Design of microstructured single-mode fiber combining large mode area and high rare earth ion concentration

We propose a new design of microstructured fiber combining large doped area (500 μm2), high rare earth concentration and single mode propagation despite the high core refractive index (nSi + 0.01). Actually, original guiding properties, based on a total internal reflection guidance regime modified by coupling between core and resonant cladding modes (close to the ARROW model) ensure single mode propagation. Moreover spectral properties which are largely governed by characteristics of high index cladding rods can be adjusted by properly choosing diameter and refractive index of the rods.

Single-mode laser emission from a multimode core surrounded by a tailored cladding

We report the transversally-single-mode laser emission from a large ytterbium-doped core exhibiting a normalized frequency of 7.25. Strong interaction between the core and an array of high refractive index rods leads to single-mode emission.

Microstructured fibres and applications

In this paper, we explore some new concepts of optical fibre designs exhibiting large active core surrounded by resonant cladding for high power delivery.

Tunable laser in the green, red and near IR by frequency mixing of a dual wavelength Er/Yb co-doped fiber laser

We report a tunable laser source emitting in the visible (530 nm, 630 nm) and the near infrared (775 nm, 1060 nm, and 1550 nm) regions by frequency summation of a dual wavelength Er/Yb co-doped fiber laser.

Alternative designs for high power single mode active optical fibres

In this paper, we propose, through different theoretical examples of composite fibre designs, some alternative ways to push up the limits of active optical fibres. Highly ytterbium-doped large cores are required for high power delivery and low non linear limitations. Such cores usually support several guided modes. We demonstrate in this paper that by surrounding the core with a tailored cladding, single mode transverse emission under amplification or in the lasing regime is possible. A 3D modelling of transverse mode competition in active fibres is first presented and applied to several cladding designs. This numerical model, which is wavelength sensitive, is of great interest for laser cavity design in continuous wave regime for example as both composite fibre and cavity designs are considered. Accurate modelling of modal competition requires to compute overlap between electric field and active region for each electromagnetic mode (Γmn) as a function of the transverse plane coordinates Γmn(x, y). The fibre design, the laser cavity, the pump power have to be considered in order to obtain an accurate description of 3D spatial population inversion and its consequences on modal competition under active regime. The numerical model is first applied to a fibre exhibiting an all solid cladding made of 2D array of high refractive index rods and then to a multi-layered fibre. The latter is used to illustrate our purpose in figure 1 which shows the comparison between lasers made of fibres with or without tailored cladding. Both fibres exhibit an Yb-doped (5625 wt-ppm) core with a diameter of 30 µm and a refractive index higher than that of silica (5×10−3). The pump power is 60 W. When the core is surrounded by pure silica, 17 modes can propagate and LP01 carries less than 20% of the total output power which is distributed among almost all modes (Fig. 1b). The laser obtained is highly multimode and the spatial quality of the beam is expected to be very low. On the contrary, when the structured cladding surrounds the core (Fig. 1a), almost all the laser power is emitted on the LP01 mode (Fig. 1c). With a 4% – 99%, 2 m long cavity, less than 8% of total power is emitted on the LP41, all other modes do not exist.

BPM-Numerical Study of Microstructured Fiber With High Difference Index Profile

A scalar beam propagation method is used to study confinement losses of air-clad fibers versus their geometrical parameters. The method is also applied to the computation of multimode guidance and pump absorption in two different microstructured fibers with high refractive index difference.

Optical Fiber Design And Fabrication: Discussion On Recent Developments

Level of emitted power and beam quality of singlemode fiber lasers have been drastically increased at the expense of loss due to bend sensitivity, simplicity of manufacturing and packaging. Furthermore, the extension of the spectral coverage was primarily explored by exploiting non‐linear effects, neglecting numerous possible transitions of rare earths. Through different research areas, we demonstrate the possibilities offered by new fiber designs and alternative methods of manufacturing. Photonic Band Gap fibers reconcile diffraction limited beam and large mode area with low bending loss. 80% slope efficiency is demonstrated together with a robust propagation allowing the fiber to be tightly bent until wounding radii as small as 6 cm. Highly ytterbium doped multimode core surrounded by high refractive index rods fiber exhibits a transverse singlemode behavior under continuous wave laser regime. A robust LP01 mode is observed and filtering effect is clearly observed. A non CVD process based on silica sand...

Design of large and highly doped core microstructured fiber for single-mode operation and high pump absorption

We propose a new microstructured fiber design combining large and highly doped area, low bend loss, high pump absorption and single-mode propagation. An original guiding regime is governed by characteristics of high index cladding rods.