Modified and double-clad large mode-area leakage channel fibers for extreme temperature conditions

摘要

Recently large-mode-area hybrid leakage channel fibers (HLCFs) were reported to overcome the limitation on mode area with single-mode (SM) operation for the practical bending radius of 7.5 cm at the preferred wavelength of 1064 nm. In this paper, we present the effects of a thermally induced refractive index change on the mode area of bend-compensated extremely LMA modified HLCFs (M-HLCFs) and double-clad M-HLCFs. A full-vectorial finite-element method-based modal solver is used to obtain the modal characteristics of M-HLCFs in various heat load conditions. Numerical simulations reveal that the effective mode area of M-HLCFs is similar to 1433 mu m(2) at room temperature, which marginally decreases to similar to 1387 mu m(2) while SM operation is maintained when the temperature distribution rises to similar to 125 degrees C over the fiber geometry during high-power operations. We have also investigated a double-clad M-HLCF design exhibiting a mode area > similar to 1000 mu m(2) for all heat load density variations up to a maximum of 12 x 10(9) W m(-3), corresponding to a 250 degrees C temperature in the center of the fiber core region.