Ultrathin Metal–Organic Framework: An Emerging Broadband Nonlinear Optical Material for Ultrafast Photonics

摘要

Crystalline porous metal–organic frameworks (MOFs) with nanometer-sizedrnvoid spaces, large surface areas and ordered reticular motifs have offered arnplatform for achieving disruptive successes in divisional fields. Great progress inrnexploring the linear and nonlinear optical features of MOFs has been achieved,rnyet third-order optical nonlinearities in two-dimensional (2D) MOFs have rarelyrnbeen studied. Here, a broadband nonlinear optical amplitude modification andrnphase shift are demonstrated in a few-layer nickel-p-benzenedicarboxylic acidrnMOF (Ni-MOF). The calculated bandgap of Ni-MOF decreases from 3.12 eV torn0.85 eV as the doping of Ni ions increases, indicating the ability of this materialrnto be used for optical amplitude modulation from the visible to the near-infraredrnregion, which is experimentally confirmed via a Z-scan technique. The determinedrnthird-order optical nonlinearities resemble those of other low-dimensionalrnnonlinear optical materials, suggesting the wide potential of Ni-MOF for applicationrnin optoelectronics. As an example, a Ni-MOF-based saturable absorber wasrnimplemented into fiber resonators to demonstrate its broadband mode-lockingrnoperations. A femtosecond laser pulse was readily obtained in the telecommunicationrnwavelength window in an integrated all-fiber resonator. Considering thernchemical compatibility and rich variability, these primary investigations pave thernway towards advanced photonics based on multifeature MOF materials.