Innovative multimode step-index fibers for improved transmission of blue and green laser radiation

Multimode step-index fused silica fibers with an undoped silica core and fluorine-doped cladding are widely used for high-power laser delivery due to their robust all-silica design. In this work, we present newly developed preform materials that provide excellent transmission performance across the 300 nm to 850nm wavelength range, enabling efficient delivery of blue and green laser radiation for applications such as copper and brass welding. High-power laser exposure, particularly with pulsed sources, can induce structural changes and defect formation in the glass matrix, leading to increased attenuation and potential fiber failure. Therefore, developing fiber materials that maintain stability under extreme conditions is critical. This paper compares the optical transmission properties of the new materials with conventional fibers and reports results from high-power nanosecond-pulsed laser tests at 355nm. The new fibers exhibited no measurable degradation during extended irradiation, demonstrating their outstanding resistance to laser-induced aging and confirming their suitability for demanding industrial and scientific applications.