Modeling thermo-optic effect in large mode area double cladding photonic crystal fibers

Coscelli, Enrico; Cucinotta, Annamaria

doi:10.1142/s0217979214420028

Cited by 8 publications

(5 citation statements)

References 23 publications

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“…The above mentioned have explained that even intrinsically single-mode fibers can generate multimode behavior when they are under severe heat load. Similar conclusions have been reported in the early literature [26][27][28][29]. Nevertheless, to our knowledge, most of them have ignored the variation of the axial heat load distribution, and only considered the average heat load instead.…”

Section: Numerical Analysis Of Thermal Effects On Mode Propertiessupporting

confidence: 87%

Thermo-optic behaviour of intrinsically single-mode low-numerical aperture (NA) ytterbium-doped fibre

et al. 2019

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A simplified model based on the finite-element method is proposed to study the thermo-optic behavior in high-power fiber amplifiers. It is shown that thermally induced refractive index change results in a thermal lens effect and ultimately leads to multimode behavior even in an intrinsically single-mode fiber. Besides, experimental investigations were carried out to characterize the thermo-optic behavior of an intrinsically single-mode large mode area 20/400 ytterbium-doped fiber with core numerical aperture (NA) ~ 0.04 in an all-fiber amplifier. Output power up to 1.68 kW was achieved with a deterioration of beam quality from M 2 < 1.1 to 1.7. It is explained that due to the uneven distribution of axial heat load, an intrinsically singlemode fiber gradually turns into a combination of a multi-mode fiber and a single-mode fiber with the growing heat load and then the leakage core modes trigger transverse mode instability. Moreover, a near diffraction-limited output power of 1.35 kW from an all-fiberized low-NA fiber amplifier is obtained.

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Section: Numerical Analysis Of Thermal Effects On Mode Propertiessupporting

confidence: 87%

Thermo-optic behaviour of intrinsically single-mode low-numerical aperture (NA) ytterbium-doped fibre

et al. 2019

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“…1(d), has an all-solid cladding with a raisedindex pedestal (n = 1.457) matched with the gain medium and pure silica inclusions, carefully placed to avoid any mirror or rotational symmetry, to replace the air-holes. The guided modes of the fibers have been calculated, for a wavelength of 1032 nm, with a commercial full-vector modal solver based on the finite-element method [23], which was also used to solve the steady-state heat equation to obtain the thermally-induced refractive index change over the crosssection [20], [24]. The implemented model operates in two steps.…”

Section: Modeling Of Lma Pcfsmentioning

confidence: 99%

Analysis of the Modal Content Into Large-Mode-Area Photonic Crystal Fibers Under Heat Load

Coscelli

Dauliat

Poli

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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Thanks 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.

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“…23 The cross-section of the two PCFs is enclosed by a 7 μm thick air-cladding, whose diameter d AC has been changed in the simulations between 15Λ and 21Λ. A full-vector modal solver based on the finite-element method has been used to solve the steady-state heat equation to obtain the thermally-induced refractive index change over the cross-section 24,25 and, then, to calculate the guided modes at a wavelength of 1032 nm. Quantum defect heating of the core and convective cooling at the outer edge cause a temperature gradient along the cross-section, which is responsible for the creation of a refractive index profile with maximum in the core center, parabolic shape in the core and logarithmic decay in the cladding.…”

Section: Modeling Of Lma Dc-pcfsmentioning

confidence: 99%

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

et al. 2016

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Constant innovations of fiber technology over the last twenty years has fueled a huge improvement of the performances of fiber lasers. Further power scaling of fiber lasers is currently hindered by the phenomenon of transverse mode instabilities, a sudden deterioration of output beam quality occurring beyond a certain power threshold due to energy transfer from the fiber fundamental mode to high-order modes. Several studies have pinpointed a thermal origin for this phenomenon. A possible solution is to implement fiber designs capable of providing a robust single-mode operation even under severe heat load, in order to prevent such coupling. In this paper the effects on the propagating modes of the change of the inner cladding size and microstructuration in double-cladding photonic crystal fibers under heating condition are discussed, and related to field confinement and single-mode regime.

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Modeling thermo-optic effect in large mode area double cladding photonic crystal fibers

Cited by 8 publications

References 23 publications

Thermo-optic behaviour of intrinsically single-mode low-numerical aperture (NA) ytterbium-doped fibre

Thermo-optic behaviour of intrinsically single-mode low-numerical aperture (NA) ytterbium-doped fibre

Analysis of the Modal Content Into Large-Mode-Area Photonic Crystal Fibers Under Heat Load

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

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