Design and Characterization of a Polarizing Microstructured Optical Fiber with Large Mode Area for Single-Mode Operation at 1064 nm

International audience; The single-mode (SM) ytterbium-doped fibers with large mode area (LMA) have attracted much attention to increase the power of fiber lasers and amplifiers. The power level of pulsed fiber lasers in the range of a few tens of watts to multi-kilowatts have been demonstrated but still need to be enhanced for industrial applications. A major limitation to the development of higher output power is nonlinear effects, which can be overcome by using LMA fibers in order to maintain an acceptable output-beam quality. Compared to conventional fibers, microstructured optical fibers (MOF) provide much better control of numerical aperture to values as low as 0.02, which allows a core diameter greater than 100 µm while keeping SM operation. Furthermore, the possibility to insert stress rods able to modify the polarization properties of MOFs is of great interest for those applications, which require the use of polarization maintaining (PM) or polarizing fibers. However, weak guidance makes LMA MOFs very bend sensitive, forcing them to be kept straight for core diameters above 45 µm. Recently, a promising fiber design with better bending loss performance has been reported by Dong et al. Theoretical studies of these fibers relate only to non-PM fibers. In this work, we numerically investigate the influence of stress-rods on bending losses of guided modes in passive LMA MOFs at 1064 nm, using a method based on the finite element method. Experimental performances of fabricated 50-µm core diameter polarizing fiber are also presented.