Top-hat beam output of a single-mode microstructured optical fiber: Impact of core index depression

Valentin, C.; Calvet, Pierre; Quiquempois, Yves; Bouwmans, Géraud; Bigot, Laurent; Coulombier, Quentin; Douay, M.; Delplace, Karen; Mussot, Arnaud; Hugonnot, Emmanuel

doi:10.1364/oe.21.023250

Cited by 38 publications

(29 citation statements)

References 25 publications

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“…~50% larger than that of a regular LCF with the same core [6]. The flat-top mode in this work is the largest even demonstrated, with ~6 times the effective mode area of the record demonstrated previously [5]. A 6m-long fiber was tested in a laser configuration, showing a slope efficiency of ~84% at 1026 nm with respect to the absorbed pump power at 976 nm.…”

Section: Introductionmentioning

confidence: 48%

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50μm-core Yb-doped leakage channel fiber with flattened mode

Kong

Hawkins

et al. 2014

Laser Technology for Defense and Security X

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Power scaling of fiber lasers is highly desirable in many applications but is mainly limited by nonlinear effects. Largemode-area fibers have been used to mitigate this limit, such as the leakage channel fiber (LCF). The mode intensity profile in these fibers typically exhibits Gaussian-like structure with much reduced effective mode-area compared to the physical fiber core area. Thus, a flat-top mode with a uniform intensity distribution is more suitable for larger effective mode-area without having to increase core size. In this work, we demonstrate the first flat-top mode generated in a 50 µm-core Yb-doped LCF fiber. The mode flattening from Gaussian beam to a flat-top one is achieved by using a 30 µm uniform Yb-doped area in the core center with a refractive index very slightly below that of the background silica glass by 2×10 -4 . The resulting flat-top mode has a significantly increased effective mode area of ~1880 um 2 , which is ~50% larger than that of a conventional uniform core and ~6 times the effective mode area of the flat-top mode record demonstrated previously. A 6m-long fiber is also tested in a laser configuration with a slope efficiency of ~84% at 1026 nm with respect to the absorbed pump power at 976 nm.

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Section: Introductionmentioning

confidence: 48%

“…Thus, a flat-top mode with a uniform intensity distribution is more suitable for larger effective mode-area. It has been shown that a flat-top mode can increase the effective mode area by ~60% without having to increase core size [3,4,5]. The flat-top mode is also of benefit in marking and material processing applications.…”

Section: Introductionmentioning

confidence: 99%

50μm-core Yb-doped leakage channel fiber with flattened mode

Kong

Hawkins

et al. 2014

Laser Technology for Defense and Security X

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“…Such electric field distribution could be useful for high power applications [12], [13]. We note that this mode electric field is not possible with real refractive index profile fibers, the exponential decay being more in the realm of slab dielectric waveguiding.…”

Section: Numerical Results and Discussionmentioning

confidence: 96%

Design of Arbitrary Modal Electric Field in Cylindrical Waveguides

Boucouvalas

Thraskias

2014

IEEE J. Quantum Electron.

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In this paper, we examine for the first time how to design arbitrary shape modal fields within complex refractive index circular waveguides. In order to achieve this flexibility in field shape, we use complex refractive index profile waveguides, where we determine the required refractive index profile on both real and imaginary refractive index. We develop a technique for calculating directly and accurately the refractive index profiles of cylindrical waveguides from knowledge of the desired modal electric field. The method we use to solve this inverse problem is via modeling the waveguide transversely as a transmission line. We demonstrate this algorithm with a number of example reconstructions of different arbitrary modal electric fields. The refractive index profiles generated supporting the required modal electric fields are complex. We reconstruct complex refractive index profiles which support unusual electric field distributions. We expect this technique to be useful in designing special fibers for mode matching between dissimilar waveguides, in designing sensing optical fibers, in mode division multiplexing, in gain flattening optical fiber amplifiers, and also for high power optical fibers.

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“…1(d) shows the normalized electric field of FM at different wavelengths. It is interesting to note that at shorter wavelength, FM looks like a ring mode and with increasing wavelength the effective refractive index of mode decreases and it appears like a flat-top mode, thanks to the spreading electric field in the core region with increasing wavelength [5]. This flat-field leads to a very large effective area for the FM.…”

Section: Fiber Design and Working Principlementioning

confidence: 97%

“…It is interesting to see that due to the flat-top profile, it can also be used for several material processing applications such as welding, drilling, cutting, marking etc, where Gaussian beam profile is not good enough. PCF based designs with a flat-top output beam profile have been reported previously [5][6]. However, these designs are difficult to fabricate and reported area is lower than 2,000µm 2 .…”

Section: Fiber Design and Working Principlementioning

confidence: 99%