The hologram is an ideal method for displaying three-dimensional images visible to the naked eye. Metasurfaces consisting of subwavelength structures show great potential in light field manipulation, which is useful for overcoming the drawbacks of common computer-generated holography. However, there are long-existing challenges to achieving dynamic meta-holography in the visible range, such as low frame rate and low frame number. In this work, we demonstrate a design of meta-holography that can achieve 228 different holographic frames and an extremely high frame rate (9523 frames per second) in the visible range. The design is based on a space channel metasurface and a high-speed dynamic structured laser beam modulation module. The space channel consists of silicon nitride nanopillars with a high modulation efficiency. This method can satisfy the needs of a holographic display and be useful in other applications, such as laser fabrication, optical storage, optics communications, and information processing.

Memristor is regarded as one of the key devices to break through the traditional Von Neumann computer architecture due to its capability of simulating the function of neural synapses. And...

Characterizing the physical and chemical properties of two-dimensional (2D) materials is of great significance for performance analysis and functional device applications. As a powerful characterization method, nonlinear optics (NLO) spectroscopy has been widely used in the characterization of 2D materials. Here, we summarize the research progress of NLO in 2D materials characterization. First, we introduce the principles of NLO and common detection methods. Second, we introduce the recent research progress on the NLO characterization of several important properties of 2D materials, including the number of layers, crystal orientation, crystal phase, defects, chemical specificity, strain, chemical dynamics, and ultrafast dynamics of excitons and phonons, aiming to provide a comprehensive review on laser-based characterization for exploring 2D material properties. Finally, the future development trends, challenges of advanced equipment construction, and issues of signal modulation are discussed. In particular, we also discuss the machine learning and stimulated Raman scattering (SRS) technologies which are expected to provide promising opportunities for 2D material characterization.

The precise placement of semiconductor nanowires (NWs) into two- or three-dimensional (2D/3D) micro-/nanoarchitectures is a key for the construction of integrated functional devices. However, long-pending challenges still exist in high-resolution 3D assembly of semiconductor NWs. Here, we have achieved directional assembly of zinc oxide (ZnO) NWs into nearly arbitrary 3D architectures with high spatial resolution using two-photon polymerization. The NWs can regularly align in any desired direction along the laser scanning pathway. Through theoretical calculation and control experiments, we unveiled the laser-induced assembly mechanism and found that the nonoptical forces are the dominant factor leading to the directional assembly of ZnO NWs. A ZnO-NW-based polarization-resolved UV photodetector of excellent photoresponsivity was fabricated to demonstrate the potential application of the assembled ZnO NWs. This work is expected to promote the research on NW-based integrated devices such as photonic integrated circuits, sensors, and metamaterial with unprecedented controllability of the NW’s placement in three dimensions.

Intelligent micromachines that respond to external light stimuli have a broad range of potential applications, such as microbots, biomedicine, and adaptive optics. However, artificial light-driven intelligent micromachines with a low actuation threshold, rapid responsiveness, and designable and precise 3D transformation capability remain unachievable to date. Here, a single-material and one-step 4D printing strategy are proposed to enable the nanomanufacturing of agile and low-threshold light-driven 3D micromachines with programmable shape-morphing characteristics. The as-developed carbon nanotube-doped composite hydrogel simultaneously enhanced the light absorption, thermal conductivity, and mechanical modulus of the crosslinked network, thus significantly increasing the light sensitivity and response speed of micromachines. Moreover, the structural design and assembly of asymmetric microscale mechanical metamaterial unit cells enable the highly efficient additive nanomanufacturing of 3D shape-morphable micromachines with large dynamic modulation and spatiotemporal controllability. Using this strategy, the world's smallest artificial beating heart with programmable light-stimulus responsiveness for the cardiac cycle is successfully printed. This 4D printing method paves the way for the construction of multifunctional intelligent micromachines for bionics, drug delivery, integrated microsystems, and other fields.

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Quasi-1D titanium trisulfide (TiS3) has strong in-plane anisotropy with a direct band gap of about 1 eV, which has attracted wide attention in the fields of microelectronics and optoelectronics. However, the investigation of in situ synthesis, synthetic mechanism, and nonlinear optical properties of TiS3 is rarely reported. In this work, we developed a transfer-free method to grow TiS3 nanoribbons, successfully reducing the synthesis time from a few days to less than 24 h without pretreatment. Raman spectroscopy revealed TiS3 was not directly synthesized by titanium (Ti) and sulfur (S) but by the further sulfurization reaction of intermediate product TiS2. Moreover, the polarized four-wave mixing (FWM) imaging of the as-grown TiS3 samples was conducted by ultrafast nonlinear optical spectroscopy for the first time, identifying the crystal axis orientation of TiS3 accurately and quickly. Our work not only provides a rapid growth method for transfer-free synthesis of TiS3 nanoribbons on SiO2/Si substrates but also investigate the fast and non-destructive ultrafast nonlinear optical characterization of quasi-1D TiS3, which lays a foundation for understanding the synthetic mechanism and physicochemical properties of transition metal trisulfides (TMTCs) and promoting the functional device applications of TMTCs represented by TiS3.