Spectrally Reconfigurable Multi-Wavelength Raman Fiber Laser With up to 15.29 THz of Tuning Range

Multi-wavelength Raman fiber lasers provide a flexible and controllable option for applications such as generation of terahertz radiation, deep-tissue bioimaging and so on. However, conventional multi-wavelength Raman fiber lasers employing silica fiber as the gain medium are constrained by the narrow Raman gain spectrum, which limits their tunability. Here, we present a broadly tunable multi-wavelength Raman fiber laser utilizing a phosphosilicate fiber as the gain medium for the first time. By integrating an acousto-optic tunable filter, the system achieves efficient multi-wavelength lasing with flexible wavelength selection and wavelength-dependent loss control. This capability enables precise and dynamic spectral reconfiguration, including single-wavelength tunable emission at the 1.1 μm band over a broad frequency shift range of 15.29 THz (2.85-18.14 THz), dual-wavelength separation tunable emission with gap-free tuning and adjustable spectral shaping, and simultaneous output of up to five wavelengths. To validate the superior gain bandwidth of phosphosilicate fiber compared to silica fiber, we replaced the phosphosilicate fiber with silica fiber and observed a significantly reduced frequency shift range of 7.23 THz (7.89-15.12 THz), less than half that of phosphosilicate fiber. We believe the developed multi-wavelength Raman fiber laser with reconfigurable spectrum can provide a compact, flexible, and easily-tunable platform for potential applications in nonlinear frequency conversion, temporal ghost imaging across various spectral bands.