Optimization of Cascaded Raman Stokes Generation Using Effective Area Variations in Optical Fibers

Abstract

By introducing discontinuities in the effective area of the optical fiber through the splicing of a short fiber segment, the performance of a cascaded Raman laser system has been significantly improved. By incorporating a 46 cm thin-core Nufern 980HP fiber between two spans of larger-core Corning MetroCor fiber, we achieved enhanced output power and conversion efficiencies for the Stokes signals. Specifically, conversion efficiency improvements of ∼ 26.20%, ∼39.21%, and ∼ 82% were observed for the 2nd, 3rd, and 4th Stokes, respectively. Additionally, the Raman threshold was reduced, resulting in a pumping power requirement reduction of ∼ 14.8% and ∼ 13.6% for the 2nd and 3rd Stokes. Our results confirm that this simple and cost-effective approach enables significant improvements in Raman gain medium performance, offering new pathways for energy-efficient Raman fiber lasers for applications in Medicine, spectroscopy, biomedical imaging, remote sensing, and Telecomm.