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

Two nonlinear optical fluoride carbonate crystals (Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2) have been synthesized under subcritical hydrothermal condition. Both crystals crystallize in the noncentrosymmetric space group Cc (No. 9). The structure of Na8Lu2(CO3)6F2 with high density of [CO3] groups is described as 1D [Na5Lu(CO3)2F2] chains connected by [CO3] triangles, forming an intricate three-dimensional framework. Lu3+ and Na+ cations are alternatively ordered and disordered in the cavities of the 3D network. The structure of Na3Lu(CO3)2F2 is built up from the [NaLu(CO3)2F2] layers which are separated by other Na+ cations. The [CO3] anionic groups arrange approximately coparallel to the plane. The second harmonic generation (SHG) measurement indicates that Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2 have large SHG responses that are approximately 4.29 and 4.21 times KH2PO4 (KDP), respectively. The responses are also phase-matchable in the visible region. In addition, it exhibits wide transparent regions ranging from UV t...

Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2: Rare Earth Fluoride Carbonates as Deep-UV Nonlinear Optical Materials

A new alkali-metal borogermanate with noncentrosymmetric structure, namely, Cs2GeB4O9, has been discovered, and a large crystal with dimensions of 20 × 16 × 8 mm3 has been grown by a high-temperature top-seeded solution method using Cs2O–B2O3 as a flux. The compound crystallizes in the tetragonal space group I4 with a = b = 6.8063(2) A, c = 9.9523(7) A, V = 461.05(4) A3, and Z = 2. It features a three-dimensional anionic open framework based on GeO4 tetrahedra and B4O9 clusters that are interconnected via corner-sharing, forming one-dimensional channels of nine-/ten-membered rings along the a and b axes, which are occupied by Cs+ cations. Cs2GeB4O9 exhibits a very high thermal stability with a melting point of 849 °C, and it possesses a short-wavelength absorption edge onset at 198 nm determined by UV–vis transmission spectroscopy measurements on a slab of polished crystal. Powder second-harmonic generation (SHG) measurement on sieved crystals reveals that Cs2GeB4O9 is a type I phase-matchable material w...

Cs2GeB4O9: a New Second-Order Nonlinear-Optical Crystal

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.

Single crystals of LuAl3(BO3)4 (LuAB) have been grown with the top-seeded solution growth method from a new tungstate based flux Li2WO4–B2O3. The crystallization region of LuAB is revealed in a quasi-ternary system of LuAB–Li2WO4–B2O3. Correlation between the crystallization region of LuAB and an excess of Al2O3 in the flux system has been identified for the first time. Compared with the commonly used K2Mo3O10–B2O3 flux at 1100 °C, the Li2WO4–B2O3 flux has lower volatility with lower incorporation of tungstate into the crystals. Thermophysical properties of the crystal have been investigated for the first time, where the thermal expansion coefficients along two crystallographic directions in the temperature range of 30–800 °C were determined to be α1 = 3.38 × 10–6 K–1 and α3 = 10.4 × 10–6 K–1. The specific heat was about 0.65 J/(g·K) at room temperature. The thermal conductivities at room temperature were 12.47 W/(m·K) and 10.443 W/(m·K) along the a and c axes, respectively, and the Vickers hardness value...

Growth and Thermophysical Properties of the Nonlinear Optical Crystal LuAl3(BO3)4

The optical properties of pure LuAl3(BO3)4 (abbreviated as LuAB) crystals were investigated for the first time. Large UV-transparent LuAl3(BO3)4 crystals were grown by a high-temperature top-seeding method with Li2WO4O7-B2O3 as the flux. The refractive indices of LuAl3(BO3)4 at several wavelengths covering ultraviolet-visible and near-infrared regions were measured by the auto-collimation method. The parameters of Sellmeier’s dispersion equation were determined from the experimental data. The phase-matching curve of second harmonic generation was measured. The nonlinear optical coefficient d11 of LuAB crystal was determined to be 1.10 pm/V by a phase-matching method. The UV cut-off wavelength of the LuAl3(BO3)4 crystal was shorter than 190 nm.

Growth and optical properties of nonlinear LuAl_3(BO_3)_4 crystals

Design of a New Ultraviolet Nonlinear Optical Material KNO3SO3NH3 Exhibiting an Unexpected Strong Second Harmonic Generation Response

A novel fluorosulfate, K2(BeS)O4F2, is successfully synthesized via introducing non-π-conjugated polar tetrahedra [(BeS)O3F]. Its structure features unprecedented 1D isolated [(BeS)O4F2]∞ chains connected by KO2F3 pyramid. Owing to the polar [(BeS)O3F]...

Shenghao Fang

Papers

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

Growth and Thermophysical Properties of the Nonlinear Optical Crystal LuAl3(BO3)4

Growth and optical properties of nonlinear LuAl_3(BO_3)_4 crystals

Design of a New Ultraviolet Nonlinear Optical Material KNO3SO3NH3 Exhibiting an Unexpected Strong Second Harmonic Generation Response

K2(BeS)O4F2: A novel fluorosulfate with unprecedented 1D [(BeO3F)-(SO3F)]∞ chains exhibiting large birefringence