Optical active Pancharatnam–Berry coding metasurfaces for amplitude modulation of terahertz beams.

MXenes, a new class of 2D transition metal carbides, nitrides, and carbonitrides, have attracted much attention due to their outstanding properties. Here, we report the broadband spatial self-phase modulation of Ti 2 CT x MXene nanosheets dispersed in deionized water in the visible to near-infrared regime, highlighting the broadband nonlinear optical (NLO) response of Ti 2 CT x MXene. Using ultrafast pulsed laser excitation, the nonlinear refractive index n 2 and the thirdorder nonlinear susceptibility χ 3 ð Þ monolayer of Ti 2 CT x MXene were measured to be $10 −13 m 2 /W and $ 10 −10 esu, respectively. Leveraging the large optical nonlinearity of Ti 2 CT x MXene, an all-optical modulator in the visible regime was fabricated based on the spatial cross-phase modulation effect. This work suggests that 2D MXenes are ideal broadband NLO materials with excellent prospects in NLO applications. K E Y W O R D S2D materials, all-optical modulator, MXene, spatial cross-phase modulation, spatial self-phase modulation # These authors contribute equally to the work.

Jumping crystals, as newly emerging crystal materials that can effectively convert non-kinetic energy into kinetic energy to jump, have attracted great research interest lately. Existing jumping crystals are discovered by accident or designed based on the principle that generates force through lattice deformation, whereas in this contribution, we propose a de novo concept to design versatile jumping crystals by simply introducing a “jumping-mate” (an easily escaping component under stimuli), which is more reliable and achievable. A charge transfer complex of coronene and tetrafluoro-1,4-benzoquinone was constructed as a proof-of-concept, which showed various jumping behaviors (including directional jumping) and reversible ON/OFF switching of luminescence under thermal stimuli. The rare dynamic internal conversion between electronic and optical functions was also realized in our system. Our findings may guide the creation of a new generation of advanced multi-functional jumping crystals.