Zhonglin Li

Optical elements for polarization control, including polarizers and waveplates, are crucial for quantum optics, sub‐diffraction imaging, and biomedical sensing. Polarization state modulators based on metasurface enable miniaturized, ultrathin, and highly integrated optical components; however, their geometry‐encoded functionality limits multifunctional integration. Here, a single‐port Fabry‐Pérot cavity resonance system is designed based on atomically thin MoS ₂ supported on a ZnO/SiO ₂ /Si substrate, which enables significant reflective phase modulation arising from phase singularities. Both theoretical and experimental results demonstrate that monolayer MoS ₂ supported on a ZnO(30 nm)/SiO ₂ (300 nm)/Si substrate can convert 45° linearly polarized incident light into 0° linearly polarized reflected light, circularly polarized reflected light, and a highly linearly polarized reflected state with a polarization orientation of 135°, depending on the incident angle and operating wavelength. Through appropriate control of structural parameters, including film thickness and incident angle, this resonant system can realize three polarization functionalities, acting as a linear polarizer, a quarter‐wave plate, and a half‐waveplate. The operating wavelength range, degree of linear polarization, and degree of circular polarization are systematically analyzed. This MoS ₂ ‐based resonant system features a simple structure and versatile polarization modulation capabilities, providing guidance for the design and fabrication of planar integrated optical components.

Controlling polariton dispersion facilitates the study of various new physical phenomena, such as Bose‐Einstein condensation, polariton lasing, and coherent quantum fluid dynamics, with manual control remaining an area of ongoing exploration. In this work, monolayer MoS ₂ based Fabry‐Pérot microcavity is used to form polaritons. Five types of Bravais lattices based on polymethyl methacrylate (PMMA) nanopillars are intentionally designed. The energy overlap between the periodic PMMA scattering wave and the polariton establishes a coupling channel that controls the directional flow of polaritonic energy, as demonstrated through angle‐resolved reflectance measurements. Back‐space image measurements further demonstrate that the dispersion in reciprocal space can be directly and manually tuned, allowing for control over their number and their positions. The coupling between the polariton and PMMA scattering wave is further demonstrated by analyzing the reflectance using temporal coupled‐mode theory. The symmetries of 2D Bravais lattices allow the angle between energy and momentum flow to vary widely, and the position of the dispersion branch in a specific direction can be fine‐tuned via lattice constant, enabling full‐range control over polariton dispersion. This work presents the first theoretical and experimental demonstrations of guiding the direction of polaritonic energy and momentum through Bravais lattice design.

As an elemental crystal, anisotropic two-dimensional (2D) tellurium (Te) flakes have recently garnered significant attention due to their exceptional chemical stability, tunable bandgap, low thermal conductivity, and high carrier mobility. To further investigate the anisotropic properties of Te nanoflakes, a rapid and effective method of determining their crystal axes is essential. In this study, it is demonstrated that the intensity of the Raman-active mode in Te nanoflakes exhibits a laser-polarization-dependence, varying periodically with the polarization angle. The crystal axis in two-dimensional Te nanoflakes can be identified using angle-resolved polarized Raman spectroscopy. Specifically, the Raman intensity of the A1 mode is the highest when the incident light is polarized along the [12¯10] direction and the lowest when polarized along the [0001] direction. This identification of the crystal axis via Raman spectroscopy is further verified by transmission electron microscopy measurements. In addition, theoretical simulations reveal that anisotropic Raman scattering is closely associated with the interference effect in a multilayer stacking system, as well as anisotropic absorption and anisotropic electron–phonon coupling in Te nanoflakes. This discovery not only provides a rapid method for locating the crystal axes in Te nanoflakes but also offers new insights into the scattering phenomenon in anisotropic materials beyond Te nanoflakes.

Line‐scan mode enables rapid and high‐throughput imaging through the development of an appropriate optical transverse needle focus. Diffraction gratings allow the generation of a line focus, but they face the challenge of low light power utilization due to multiple high‐order diffractions. In addition, designing the focus requires the selection of functional materials. Atomically thin transition metal dichalcogenides with high dielectric constants provide significant phase shifts to incident light by utilizing phase singularity at zero reflection. However, at zero reflection, no light power is available for utilization, necessitating a balance between phase and amplitude modulation. In this work, the aforementioned issues are addressed by designing a monolayer MoS₂ based Fresnel strip metalens. An optical needle primary focus with a transverse length of 40 µm (≈80 λ, the longest value reported to date), a sub‐diffraction‐limited lateral spot, and a broad range of working wavelengths are achieved using the metalens. The metalens not only concentrate light power in the primary diffraction order by overcoming the constraint of momentum conservation but also maintains a constant phase modulation between distinct strips. The novel method for optical manipulation present here holds great promise for applications in biology, oncology, nanofabrication, energy harvesting, and optical information processing.

Manipulation of wavefront lies at the core of next‐generation information technologies. Compared to metal and dielectric metasurfaces, atomic 2D materials exhibit excellent prospects toward fulfilling ultra‐thin thickness requirements in flat optics in wavefront shaping, with thickness much smaller than those of traditional bulky devices. However, phase manipulation by light propagating through atomic 2D materials is suppressed due to its sub‐nanometer thickness. Here, an approach is reported to realize reflection phase singularities by establishing a zero‐reflection point in a monolayer MoS₂‐based multilayer system, which broadens topological study beyond polarization singularity. This is achieved through the creation of a multilayer Fabry‐Perot‐type interference, and a pronounced phase change in the reflected light is realized due to the high absorption of monolayer MoS₂ in the studied wavelength range. As an application, a rapid, sensitive, and label‐free detection of SARS‐CoV‐2 (2019‐nCov) antigen is demonstrated with a detection limit of 10⁻¹² M L⁻¹ (62 pg ml⁻¹) by using monolayer MoS₂ based optical biosensor. In addition to offering a comprehensive study in phase singularity, efficient wavefront engineering based on the reflective system using materials is presented with atomic thickness which may greatly simplify optical architecture in flat optics, and promote its development toward compactness and integrated functions.

Structural colors based on plasmonic and dielectric nanostructures have become attractive alternatives over adsorbed dyes or pigments in high resolution color printing. The color resolution is determined by the fine‐tuning in optical resonance peak of the nanoresonators, and is strongly restricted by the limited geometrical dimensions. Here, 2D materials including MoS₂ and GaSe are demonstrated as unique materials which generate full color gamut, vivid, and extremely‐fine tuning colors. Attributed to the atomic thickness change in Fabry–Pérot cavity length and exciton‐induced additional absorption, the optical resonance peak could be tuned in the subnanometer level. As a result, the converted xy values from the reflection spectra on the CIE 1931 diagram show an average step of 0.0019 (0.0052) along x‐axis (y‐axis), with a resolution an order of magnitude higher than current plasmonic and dielectric nanoresonators. The suitability of 2D materials on submicrometer color printing is further demonstrated by fabricating color patterns using GaSe flakes and the printed image has resolutions of 50 800 lines‐per‐inch (LPI) and 25 400 dots‐per‐inch (DPI) without color mixing. The color patterns are selectively recognized by different visible light with a wavelength resolution of 20 nm. 2D materials provide new platforms for high‐resolution printing, anticounterfeiting, and high‐density spectrally encoded storage.