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

Abstract

Crystalline porous metal–organic frameworks (MOFs) with nanometer‐sized void spaces, large surface areas and ordered reticular motifs have offered a platform for achieving disruptive successes in divisional fields. Great progress in exploring the linear and nonlinear optical features of MOFs has been achieved, yet third‐order optical nonlinearities in two‐dimensional (2D) MOFs have rarely been studied. Here, a broadband nonlinear optical amplitude modification and phase shift are demonstrated in a few‐layer nickel‐p‐benzenedicarboxylic acid MOF (Ni‐MOF). The calculated bandgap of Ni‐MOF decreases from 3.12 eV to 0.85 eV as the doping of Ni ions increases, indicating the ability of this material to be used for optical amplitude modulation from the visible to the near‐infrared region, which is experimentally confirmed via a Z‐scan technique. The determined third‐order optical nonlinearities resemble those of other low‐dimensional nonlinear optical materials, suggesting the wide potential of Ni‐MOF for application in optoelectronics. As an example, a Ni‐MOF‐based saturable absorber was implemented into fiber resonators to demonstrate its broadband mode‐locking operations. A femtosecond laser pulse was readily obtained in the telecommunication wavelength window in an integrated all‐fiber resonator. Considering the chemical compatibility and rich variability, these primary investigations pave the way towards advanced photonics based on multifeature MOF materials.

Nonlinear Optical Switching in Regioregular Porphyrin Covalent Organic Frameworks

“…By comparison, in the case of Por-COF-ZnCu and Por-COF-ZnNi excited-state absorption leads to characteristic RSA behavior. [11,[16][17][18][19][20] Theswitching behavior from SA to RSA is highly interesting in view of optical switching applications. [14] In Figure 3, the red lines are the best theoretical fits to the experimental data at different input intensities.F rom the fit, we deduced the nonlinear absorption coefficient (b), ground-state absorption cross section (s o ), first excited state (s 1 ), and second excited-state absorption cross sections (s 2 ) for Por-COF-HH, Por-COF-ZnCu, and Por-COF-ZnNi (Table S1, Supporting Information).…”

Nonlinear Optical Switching in Regioregular Porphyrin Covalent Organic Frameworks

“…Moreover,t he obtained NLO absorption coefficient, b,v alue is as high as 4470 cm/GW and 4170 cm/GW for Por-COF-ZnCu and Por-COF-ZnNi, respectively;these values are higher than those of other reported materials,s uch as metalated porphyrins (b = 132-366 cm/GW), MOFs (b = 0.28-0.46 cm/GW), graphene (b = 900 cm/GW), and so on (Table S2). [11,[16][17][18][19][20] Theswitching behavior from SA to RSA is highly interesting in view of optical switching applications. [21] Moreover,t he switchover from RSA to SA behavior may be applicable in optical limiting devices based on RSA behavior at higher intensities, as well as in mode-locked lasers,because it demonstrates SA behavior at low input intensities.…”

Palladium selenide as a broadband saturable absorber for ultra-fast photonics

“…The emergency of two-dimensional (2D) layered materials provided exciting opportunities for the development of novel opto-electric, bio-medical, and energy devices [1][2][3][4][5][6][7][8][9][10][11][12][13]. Recently, novel ultra-fast optical devices such as Q-switchers, mode-lockers, optical switchers, and so on have been investigated extensively due to their excellent opto-electric characteristics including wide-absorption band, ultra-fast recovery time, high-damage threshold, etc.…”