Nonlinear-Optical Response in Zeolitic Imidazolate Framework Glass

Recently, metal-organic frameworks (MOFs) have been confirmed to be stable in a vitreous state, thus stimulating growing interest in the discovery of the physicochemical properties of these newly explored types of glasses. Herein, we examine the nonlinear-optical (NLO) response of Zn- and Zn-Co-based zeolitic imidazolate framework-62 (ZIF-62) glasses using an open-aperture Z-scan technique. We reveal that the Zn-ZIF-62 glass does not characterize a saturable absorption feature (1030 nm femtosecond laser) owing to its low optical absorption in the near-infrared (NIR) spectral region. In contrast, a NIR absorption band (1100 nm) has been observed in Zn-Co-ZIF-62 glass, which exhibits a strong NLO response with a high modulation depth of 63.85%. We attribute the observed NLO response to transient saturation of the 4T1(4F) level of Co ions upon femtosecond laser excitation. The intriguing NLO properties of this MOF glass may enable potential applications in the photonics fields for sensing and optical modulation.