Flat-top mode from a 50 µm-core Yb-doped leakage channel fiber

Abstract

We demonstrate for the first time a flat-top mode from a 50 µm-core Yb-doped leakage channel fiber (LCF). The flat intensity distribution leads to an effective mode area of ~1880 µm(2) in the straight fiber, an over 50% increase comparing to that of regular LCF with the same core diameter. The flat-top mode was achieved by using a uniform Yb-doped silica glass in the core center with an index of ~2 × 10(-4) lower than that of the silica background. The fiber was also tested in a laser configuration, demonstrating an optical-to-optical efficiency of ~77% at 1026 nm with respect to the pump at 975 nm.

The Airy fiber: an optical fiber that guides light diffracted by a circular aperture

“…As well as confirming the correct qualitative behaviour and validating the calculation leading to Fig. 10(b), this shows how the Airy fibre can be used to transport light and generate an approximate top-hat beam at the output far field, perhaps as an alternative to fibre designs that transport a top-hat beam in the near field [5,20,21].…”

Ring fiber with flat-top profile for extremely large mode area single mode operation

“…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 .…”

Industrial mJ-class all-fiber front end with spatially coherent top-hat beam output used as seeder for high power laser

“…Of course, an efficient solution is to use highly-multimode fibers [5][6][7] but it leads to a low spatial coherence inducing very low depth of focus which is often detrimental for many applications, such as cutting or marking. To overcome these drawbacks, single-mode fibers supporting a flattened fundamental mode have been developed [8][9][10][11]. Despite their promising designs, these proposed fibers were still multimode.…”