Pulse Compression in Ho:ZBLAN Photonic Crystal Fiber Using a NOLM Configuration for Ultrashort Mid-IR Generation

We propose and design a holmium-doped ZBLAN (Ho:ZBLAN) tapered photonic crystal fiber (TPCF) for generating ultrashort mid-infrared (mid-IR) pulses at 2.86 μm, utilizing a nonlinear optical loop mirror configuration (NOLM). The dispersion and nonlinear properties of the TPCF are engineered using a self-similar tapering technique, which gradually varies the core diameter and pitch along the fiber length. Initially, an undoped ZBLAN TPCF is investigated with this approach to enable the generation of low-pedestal, few-cycle ultrashort pulses at 2.86 μm. The study then extends to analyze the propagation dynamics of higher-order solitons in the Ho:ZBLAN TPCF under various low input powers, ensuring operation below the fiber’s damage threshold. This analysis captures both the self-switching behavior of the NOLM and the self-similar pulse evolution within the fiber across different power levels. By optimizing the input pump power and fiber length, we demonstrate that a 5 ps pulse at 2.8 μm can be compressed to 187 fs after propagating through 4.3 m of fiber, achieving a maximum compression factor of 26.7, a quality factor of 1.12, and a minimal pedestal energy of 0.63%.