2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

Graphene and the following derivative 2D materials have been demonstrated to exhibit rich distinct optoelectronic properties, such as broadband optical response, strong and tunable light-mater interactions, and fast relaxations in the flexible nanoscale. Combining with optical platforms like fibers, waveguides, grating, and resonators, these materials has spurred a variety of active and passive applications recently. Herein, the optical and electrical properties of graphene, transition metal dichalcogenides, black phosphorus, MXene, and their derivative van der Waals heterostructures are comprehensively reviewed, followed by the design and fabrication of these 2D material-based optical structures in implementation. Next, distinct devices, ranging from lasers to light emitters, frequency convertors, modulators, detectors, plasmonic generators, and sensors, are introduced. Finally, the state-of-art investigation progress of 2D material-based optoelectronics offers a promising way to realize new conceptual and high-performance applications for information science and nanotechnology. The outlook on the development trends and important research directions are also put forward.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202000058

2D Material Optoelectronics for Information Functional Device Applications: Status and Challenges

Recent Advances of 2D Materials in Nonlinear Photonics and Fiber Lasers

In this work, we investigate VSe2 for generating femtosecond and large energy mode-locked laser pulses for the first time. Two types of VSe2 based saturable absorbers (SAs), microfiber–VSe2 and VSe2/polyvinyl alcohol (PVA), are prepared, which exhibit strong nonlinear optical characteristics with a modulation depth (ΔT) of 22.5% and 1.849%, respectively. In contrast to other transition metal dichalcogenides (TMDCs), theoretical calculations show that VSe2 is a metallic TMDC SA. With the implementation of microfiber–VSe2, conventional soliton mode-locking Er-doped fiber (EDF) laser is demonstrated with an ultrashort pulse duration of 910 fs. Based on VSe2/PVA, a large energy EDF laser is established. The maximum single pulse energy is 25.57 nJ. This study suggests that VSe2 possesses application potential in ultrafast photonics and provides a valuable strategy for the development of TMDC based devices with desirable optoelectronic properties.

VSe2 nanosheets for ultrafast fiber lasers

Complex wave structures for abundant solutions related to the complex Ginzburg–Landau model

As a saturable absorption material, the heterostructure with the van der Waals structure has been paid much attention in material science. In general, the heterogeneous combination is able to neutralize, or even exceed, the individual material's advantages in some aspects. In this paper, which describes the magnetron sputtering deposition method, the tapered fiber is coated by the MoS2-WS2 heterostructure, and the MoS2-WS2 heterostructure saturable absorber (SA) is fabricated. The modulation depth of the prepared MoS2-WS2 heterostructure SA is measured to be 19.12%. Besides, the theoretical calculations for the band gap and carrier mobility of the MoS2-WS2 heterostructure are provided. By employing the prepared SA, a stable and passively erbium-doped fiber laser is implemented. The generated pulse duration of 154 fs is certified to be the shortest among all fiber lasers based on transition mental dichalcogenides. Results in this paper provide the new direction for the fabrication of ultrafast photon modulation devices.

Nonlinear optical properties of MoS2-WS2 heterostructure in fiber lasers.

The light field display can provide vivid and natural 3D performance, which can find many applications, such as relics research and exhibition. However, current light field displays are constrained by the viewing angle, which cannot meet the expectations. With three groups directional backlights and a fast-switching LCD panel, a time-multiplexed light field display with a 120-degree wide viewing angle is demonstrated. Up to 192 views are constructed within the viewing range to ensure the right geometric occlusion and smooth parallax motion. Clear 3D images can be perceived at the entire range of viewing angle. Additionally, the designed holographic functional screen is used to recompose the light distribution and the compound aspheric lens array is optimized to balance the aberrations and improve the 3D display quality. Experimental results verify that the proposed light field display has the capability to present realistic 3D images of historical relics in 120-degree wide viewing angle.

Time-multiplexed light field display with 120-degree wide viewing angle.

Large-scale three-dimensional (3D) display can evoke a great sense of true presence and immersion. Nowadays, most of the large-scale autostereoscopic displays are based on parallax barrier with view zone jumping, which also sacrifices much brightness and leads to uneven illumination. With a 3840 × 2160 LED panel, a large-scale horizontal light field display based on aspheric lens array (ALA) and holographic functional screen (HFS) is demonstrated, which can display high quality 3D image. The HFS recomposes the light distribution, while the ALA improves the quantity of perspective information in a horizontal direction by using vertical pixels and it can suppress the aberration that is mainly caused by marginal light rays. The 162-inch horizontal light field display can reconstruct 3D images with the depth range of 1.5 m within the viewing angle of 40°. The feasibility of the proposed display method is verified by the experimental results.

162-inch 3D light field display based on aspheric lens array and holographic functional screen.

When employing the light field method with standard lens array and the holographic functional screen (HFS) to realize the tabletop three-dimensional (3D) display, the viewing area of the reconstructed 3D images is right above the screen. As the observers sit around the table, the generated viewpoints in the middle of the viewing area are wasteful. Here, a 360-degree viewable light-field display system is demonstrated, which can present 3D images to multiple viewers in ring-shaped viewing range. The proposed display system consists of the HFS, the aspheric conical lens array, a 27-inch LCD with the resolution of 3840×2160, the LEDs array and the Fresnel lens array. By designing the aspheric conical lens, the light rays emitting from the elemental images forms the viewpoints in a ring-type arrangement. And the corresponding coding method is given. Compared with the light field display with standard lens array, the viewpoint density is increased and the aliasing phenomenon is reduced. In the experiment, the tabletop light-field display based on aspheric conical lens array can present high quality 360-degree viewable 3D image with the right perception and occlusion.

360-degree tabletop 3D light-field display with ring-shaped viewing range based on aspheric conical lens array.

Real-time terrain rendering with high-resolution has been a hot spot in computer graphics for many years, which is widely used in electronic maps. However, the traditional two-dimensional display cannot provide the occlusion relationship between buildings, which restricts the observers’ judgment of spatial accuracy. With three projectors, compound lenticular lens array and holographic functional screen, a dynamic three-dimensional (3D) light-field display with 90° viewing angle is demonstrated. Three projectors provide views for the right 30 degrees, center 30 degrees and left 30 degrees, respectively. The holographic functional screen recomposes the light distribution, and the compound lenticular lens array is optimized to balance the aberrations and improve the display quality. In our experiment, the 3D light-field image with 96 perspectives provides the right geometric occlusion and smooth parallax in the viewing range. By rendering 3D images and synchronizing projectors, the dynamic light field display is obtained.

Boyang Liu

Papers

Nonlinear optical properties of MoS2-WS2 heterostructure in fiber lasers.

Time-multiplexed light field display with 120-degree wide viewing angle.

162-inch 3D light field display based on aspheric lens array and holographic functional screen.

360-degree tabletop 3D light-field display with ring-shaped viewing range based on aspheric conical lens array.

Dynamic three-dimensional light-field display with large viewing angle based on compound lenticular lens array and multi-projectors.