Covalent Organic Framework with Polarization Dependence for Ultrafast Pulse Generation

Covalent-organic frameworks (COFs) are novel materials known for their ordered, crystalline, low-density, and porous structure, making them useful for various applications [1], [2]. In this work, a specific polarization-dependent COF named $\pi$ -electron-extended porphyrin/pyrene-linked COF (PorPh-PyTA-COF) was used as a saturable absorber (SA) for mode-locking operation in the $1.5\ \upmu\mathrm{m}$ spectral region. The mode-locked fiber laser was successfully demonstrated by leveraging this polarization dependence and saturable absorption of the COF.