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MXene is a promising two-dimensional (2D) material that is widely used in electro-photonic devices due to its unique properties. In this contribution, V2CTx, a novel MXene, was employed as a saturable absorber (SA) for hybrid passively mode-locked fiber lasers. An ultra-stable and self-starting mode-locked laser system with low threshold can be achieved using V2CTx nanosheets and nonlinear polarization evolution (NPE). Signal to noise ratio increased 13 dB compared with using only NPE SA. A 72 fs pulse duration is easily achieved from this hybrid mode-locked fiber laser system. To the best of our knowledge, this is the shortest pulse duration generated from the Yb-doped mode-locked fiber lasers using a hybrid or 2D SAs. This study proves that MXene V2CTx nanosheets can be developed as suitable SAs and served as potential advanced ultrafast photonic devices in the future.

All-optical modulators avoid the conversion from external electronic signals to optical signals and thus have the potential to achieve an energy-efficient high-speed photonic system. Phosphorene recently debuted as an attractive material that exhibits outstanding high electron mobility, strong light-matter interaction and modifiable bandgap, making it ideal for all-optical modulators. In this paper, by incorporating a phosphorene and silicon-based micro-ring resonator (MRR), we first propose and experimentally demonstrate a unique phosphorene-integrated all-optical modulator in telecommunications. By utilizing a phosphorene thin film with an average thickness of 22 nm as the absorption material, the rise time of only 479 ns and decay time of 113 ns are achieved, which is the fastest reported response time in the family of phosphorene modulators. The corresponding 3 dB bandwidth is larger than 2.5 MHz, and it exhibits a low-loss performance benefited from its finite bandgap. The proposed phosphorene/MRR hybrid modulator may have potential in the applications of all-optical interconnections.

Two-dimensional tin sulfide (SnS), as a black phosphorus-analogue binary semiconductor, has received considerable attention in photonics and optoelectronics. Herein, the third-order nonlinearity susceptibility Im χ3 is enhanced from −(6.88 ± 0.10) × 10−14 esu to −(15.90 ± 0.27) × 10−14 esu by the size-related quantum confinement in layered SnS nanosheets. Due to the energy level alignment, a phonon-bottleneck effect is observed, which leads to a prolonged carrier lifetime. These results provide a platform for actively tuning the linear and nonlinear optics, and pave the way for designing SnS-based tunable and anisotropic optoelectronic devices.

Compared with other two-dimensional materials, two-dimensional black phosphorus (BP) has attracted extensive attention across various fields including transistors, photonics, optoelectronics, sensors, batteries and catalysis in recent years owing to its high carrier mobility, wide adjustable band gap, and in-plane anisotropy. However, the instability of black phosphorus in natural environmental conditions and the chanllenges in the fabrication of large-area, high-quality semiconducting black phosphorus nanostructures seriously have hampered its rapid development in the field of nanodevices, catalysis and biophotonics. In this work, we summarize the controlled fabrication and optical properties of highly stable BP nanostructures in recent years. The research advances in photoresponse applications, including photodetectors, nonlinear and linear photonics, photocatalysis and biophotonics, are highlighted. Additionally, the challenges and opportunities of BP nanostructures in future optoelectronic devices, photocatalysis and biophotonics are discussed. [ABSTRACT FROM AUTHOR]

Controlling infrared thermal radiations can significantly improve the environmental adaptability of targets and has attracted increasing attention in the field of thermal camouflage. Thermal emitters based on Ge2Sb2Te5 (GST) can flexibly change their radiation energy by controlling the reversible phase transition of GST, which possesses fast switching speed and low power consumption. However, the feasibility of the dynamic regulation of GST emitters lacks experimental and simulation verification. In this paper, we propose an electrically tunable thermal emitter consisting of a metal–insulator–metal plasmonic metasurface based on GST. Both optical and thermal simulations are conducted to optimize the structural parameters of the GST emitter. The results indicate that this emitter possesses large emissivity tunability, wide incident angle, polarization insensitivity, phase-transition feasibility, and dynamic thermal camouflage capability. Therefore, this work proposes a reliable optimization method to design viable GST-based thermal emitters. Moreover, it provides theoretical support for the practical application of phase-change materials in dynamic infrared thermal camouflage technology. [ABSTRACT FROM AUTHOR]

The optical properties of phase‐change materials (PCMs) can be tuned to multiple levels by controlling the transition between their amorphous and crystalline phases. In multi‐material PCM structures, the number of discrete reflectance levels can be increased according to the number of PCM layers. However, the effect of increasing the number of layers on quenching and reversibility has not been thoroughly studied. In this work, the phase‐change physics and thermal conditions required for reversible switching of single and multi‐material PCM switches are discussed based on thermo‐optical phase‐change models and laser switching experiments. By using nanosecond laser pulses, 16 different reflectance levels in Ge2Sb2Te5 are demonstrated via amorphization. Furthermore, a multi‐material switch based on Ge2Sb2Te5 and GeTe with four discrete reflectance levels is experimentally proven with a reversible multi‐level response. The results and design principles presented herein will impact active photonics applications that rely on dynamic multi‐level operation, such as optical computing, beam steering, and next‐generation display technologies. [ABSTRACT FROM AUTHOR]

Cu‐exchanged low‐silica CHA zeolites (Si/Al≤4) synthesized without organic templates are promising candidate catalysts for ammonia selective catalytic reduction of nitrogen oxides (NH3‐SCR), but their practical application is restricted due to the low hydrothermal stability. Here, inspired by the transcription from duplex DNA to RNA, we synthesized Al pairs enriched low‐silica CHA zeolite (CHA‐SPAEI, Si/Al=3.7) by using silicoaluminophosphate (SAPO) featured by strict alternation of −Al−O−P(Si)−O−Al−O− tetrahedra as seed. The proportion of Al pairs in CHA−SPAEI is 78 %, which is much higher than that in the conventional low‐silica CHA (CHA‐LS, 52 %). After hydrothermal ageing at 800 °C for 6 h, Cu‐exchanged CHA‐SPAEI shows NO conversion above 90 % within 225–500 °C under a gas hourly space velocity of 200,000 h−1, which is much better than that of Cu‐exchanged CHA‐LS. The spatial close proximity of Al pairs in CHA‐SPAEI is confirmed by the 27Al double‐quantum single‐quantum two‐dimensional NMR analyses. The strict −P(Si)−O−Al−O−P(Si)−O‐ sequence in the fragments from the dissolution of SAPO seed promotes the Al pairs with the −Al−O−Si−O−Al−O− sequence via a transcription process. The utilization of aluminophosphate‐based zeolites as seeds opens up a new avenue for the regulation of the Al distribution in zeolites. [ABSTRACT FROM AUTHOR]

Wearable optical fiber sensors have great potential for development in medical monitoring. With the increasing demand for compactness, comfort, accuracy, and other features in new medical monitoring devices, the development of wearable optical fiber sensors is increasingly meeting these requirements. This paper reviews the latest evolution of wearable optical fiber sensors in the medical field. Three types of wearable optical fiber sensors are analyzed: wearable optical fiber sensors based on Fiber Bragg grating, wearable optical fiber sensors based on light intensity changes, and wearable optical fiber sensors based on Fabry–Perot interferometry. The innovation of wearable optical fiber sensors in respiration and joint monitoring is introduced in detail, and the main principles of three kinds of wearable optical fiber sensors are summarized. In addition, we discuss their advantages, limitations, directions to improve accuracy and the challenges they face. We also look forward to future development prospects, such as the combination of wireless networks which will change how medical services are provided. Wearable optical fiber sensors offer a viable technology for prospective continuous medical surveillance and will change future medical benefits. [ABSTRACT FROM AUTHOR]

Methyl acetate (MA) has a wide range of applications as an important industrial chemical. Traditional MOR zeolite for carbonylation of DME to MA accumulated carbon easily because of a 12-membered ring (12 MR) channel. In this work, we innovatively developed the method of recrystallization ferrierite (FER) zeolite using special chelating ligand sodium oleate which can affect ions other than alkali metals. The characterization results of N2 adsorption, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) show that hydrothermal recrystallization of ferrierite using sodium oleate resulted in a higher Si/Al ratio, a bigger specific surface area and a larger number of Brønsted acid sites in the eight MR channels, which was more efficient in the reaction of carbonylation of dimethyl ether than ordinary alkali treatment. [ABSTRACT FROM AUTHOR]

To further improve the performance of cavity-enhanced spectroscopy systems, a high-quality U-cavity system was established. In the process of the experiment, an asymmetric ripple effect, which is different from the previous etalon effect, was found, which seriously affects the performance of the spectral system. This unique phenomenon mainly manifests in the different amplitudes of the fluctuations of the spectral curves measured by the folding mirror and the end mirror in the U-cavity system. Based on multi-beam interference theory, we analyzed the characteristics of the transmission spectrum of each mirror in the presence of the etalon effect at the end mirror, and obtained the following conclusions: for the U-cavity system, the strength of the etalon effect of each mirror is inversely proportional to its transmission loss value, that is, the larger the loss, the smaller the ripple of the transmission spectrum, and vice versa. In order to eliminate this effect, the most effective way is to eliminate the etalon effect caused by the light feedback of the end mirror. After improving the system, the minimum detectable absorption coefficient of α min = 8.33 × 10 − 9 cm − 1 is obtained with this U-shape Optical Feedback Cavity-Enhanced Absorption Spectroscopy. These works are valuable references for the design of folded Cavity-Enhanced Absorption Spectroscopy systems and have potential for laser wavelength calibration and measurement of a mirror's reflectance. [ABSTRACT FROM AUTHOR]

Reconfigurable waveguide components are promising building blocks for photonic neural networks and as an optical analogue to field-programmable gate arrays. By changing the effective index of the waveguide, reconfigurable waveguide components can achieve on-chip light routing and modulation. In this paper, we design and demonstrate an Sb2S3-reconfigurable InP membrane Machâ€"Zehnder interferometer (MZI) on a silicon substrate. Sb2S3, which has tunable refractive index and low absorption in the near-infrared spectrum, was patterned on the InP waveguide MZIs to make an optical switch in the telecoms conventional-band. By laser induced crystallisation of the Sb2S3, it was possible to control interference in the MZI and achieve 18 dB on/off switching at 1540 nm. Laser reamorphisation and reversible switching of the Sb2S3 layer resulted in damage to the waveguide structure. However, simulations show that transition metal di-chalcogenide two-dimensional crystal layers can act as efficient thermal barriers that prevent thermal damage to the waveguide during laser amorphisation. Therefore, combining Sb2S3 with InP waveguides seems to be a feasible approach to achieve low-loss reprogrammable waveguide components for on-chip photonics routing and neural networks. [ABSTRACT FROM AUTHOR]

The spatial–temporal distribution of reactive oxygen species (ROS) in human tissue is critical for the medical applications of cold plasma jet as it reflects the therapeutic range of cold plasma jet, but the mechanism for its formation is still unclear. To this end, KI-starch reagent was used to visualize the surface distributions of ROS on the model human tissues treated by a He + O2 plasma jet in this paper. It was found that the surface distribution of ROS was divided into two parts by a small donut-shaped of un-colored area. This un-colored area was resulted from the color fading of the model tissue, which might be induced by the AC electric field of the plasma jet and the plasma-generated reductive species. The colored area and the un-colored area had different trends with the working gas flow rate and the model tissue conductivity. The un-colored area increased with the expansion of the plasma plume and shrank with the increasing model tissue conductivity. [ABSTRACT FROM AUTHOR]

Perovskite materials show exciting potential for light-emitting diodes (LEDs) owing to their intrinsically high photoluminescence efficiency and color purity. The research focusing on perovskite light-emitting diodes (PeLEDs) has experienced an exponential growth in the past six years. The maximum external quantum efficiency of red, green, and blue PeLEDs has surpassed 20%, 20%, and 10%, respectively. Nevertheless, the current PeLEDs are still in the laboratory stage, and the key for further development of PeLEDs is large-area fabrication. In this paper, we briefly discuss the similarities and differences between manufacturing high-quality and large-area PeLEDs and perovskite solar cells. Especially, the general technologies for fabricating large-area perovskite films are also introduced. The effect of charge transport layers and electrodes on large-area devices are discussed as well. Most importantly, we summarize the advances of large-area (active area ≥ 30 mm2) PeLEDs reported since 2017, and describe the methods for optimizing large-area PeLEDs reported in the literature. Finally, the development perspective of PeLEDs is presented for the goal of highly efficient and large-area PeLED fabrication. It is of great significance for the application of PeLEDs in future display and lighting. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs), a typical layered inorganic cationic material, have been widely studied as ion‐exchanger, catalyst and polymer additives. The past few decades have seen rapidly increasing interest in non‐LDH type 2‐dimensional inorganic cationic frameworks. Their novel properties derived from structural and compositional diversity cast a light on the field where LDHs show limited performance. This minireview will discuss the structure, synthesis and applications including anion‐exchange and catalysis of non‐LDH type 2‐dimensional inorganic cationic frameworks and present the prospective for researchers working on. [ABSTRACT FROM AUTHOR]

Mode-locking lasers have not only produced huge economic benefits in industrial fields and scientific research, but also provided an excellent platform to study diverse soliton phenomena. However, the real-time characterization of the ultrafast soliton dynamics remains challenging for traditional electronic instruments due to their relatively low response bandwidth and slow scan rate. Consequently, it is urgent for researchers to directly observe these ultrafast evolution processes, rather than just indirectly understand them from numerical simulations or averaged measurement data. Fortunately, dispersive Fourier transformation (DFT) provides a powerful real-time measurement technique to overcome the speed limitations of traditional electronic measurement devices by mapping the frequency spectrum onto the temporal waveform. In this review, the operation principle of DFT is discussed and the recent progress in characterizing the ultrafast transient soliton dynamics of mode-locking lasers is summarized, including soliton explosions, soliton molecules, noise-like pulses, rogue waves, and mode-locking buildup processes. [ABSTRACT FROM AUTHOR]

Cationic framework materials, especially pure inorganic cationic frameworks that can efficiently and selectively capture harmful heavy metal oxyanions from aqueous solution are highly desired yet scarcely reported. Herein, we report the discovery of a 2D cationic aluminum oxyhydroxide, JU‐111, which sets a new benchmark for heavy metal oxyanion sorbents, especially for CrVI. Its structure was solved based on 3D electron diffraction tomography data. JU‐111 shows fast sorption kinetics (ca. 20 min), high capture capacity (105.4 mg g−1), and broad working pH range (3–10) toward CrVI oxyanions. Unlike layered double hydroxides (LDHs), which are poorly selective in the presence of CO32−, JU‐111 retains excellent selectivity for CrVI even under a large excess of CO32−. These superior features coupled with the ultra‐low cost and environmentally benign nature make JU‐111 a promising candidate for toxic metal oxyanion remediation as well as other potential applications. [ABSTRACT FROM AUTHOR]

Zeolites are one of the most important heterogeneous catalysts, with a high number of large‐scale industrial applications. While the synthesis of new zeolites remain rather limited, introduction of germanium has substantially increased our ability to not only direct the synthesis of zeolites but also to convert them into new materials post‐synthetically. The smaller Ge‐O‐Ge angles (vs. Si‐O‐Si) and lability of the Ge−O bonds in aqueous solutions account for this behaviour. This Minireview discusses critical aspects of germanosilicate synthesis and their post‐synthesis transformations to porous materials. [ABSTRACT FROM AUTHOR]

All‐optical devices based on 2D materials have attracted great attention for desirable applications, such as communications and signal processing. However, the previously reported all‐fiber all‐optical devices utilizing the interferometer structures greatly limit their practical applications due to the poor anti‐interference ability and slow modulation rate. In this work, an all‐optical device has been demonstrated based on a microfiber knot resonator (MKR) deposited with Ti2CTx MXene, exhibiting a large photothermal conversion efficiency and high thermal conductivity. Experimental results show that the proposed all‐optical device is capable of producing a high‐performance phase and intensity modulation with a high modulation efficiency, fast response time, and good stability. Therefore, it is anticipated that the MKR‐based all‐optical devices based on 2D materials can pave the way to a new design of high‐performance all‐optical devices and have great potentials in the future optical information processing. [ABSTRACT FROM AUTHOR]

As a rising star of all‐carbon nanomaterial, graphdiyne (GDY) has a direct natural bandgap and features strong light–matter interaction, large optical absorption, superior chemical and optical stability, indicating its broad prospects in the field of photonics and optoelectronics. Herein, the broadband nonlinear absorption and transient absorption characteristics of GDY from visible to infrared region has been studied for the first time, and its promising application in ultrafast photonics has been explored. The large nonlinear absorption coefficient (> −1 cm GW−1), low saturation intensity (<13 GW cm−2), and ultrafast relaxation time (<30 ps) of GDY are demonstrated, which indicates the outstanding potential of GDY in photonics among the emerging novel nonlinear optical (NLO) materials. The GDY is mixed with polyvinylpyrrolidone (PVP) to prepare the GDY–PVP nanocomposite, which further improved the stability of GDY. By using the GDY–PVP nanocomposite as saturable absorption material, ultrashort pulse lasers with pulse duration of 385.5 ps and 688 fs are obtained at 1 and 1.5 µm, respectively. This work reveals the excellent nonlinear optical properties of GDY and lays a foundation for its development in advanced nanophotonic devices. [ABSTRACT FROM AUTHOR]

While black phosphorus has shown excellent optoelectronic properties in many aspects, the environmental instability ultimately places limits on its practical applications. Black arsenic–phosphorus (b‐AsP), an alloy of black phosphorus with arsenic atoms, has emerged as a new 2D material with better stability. Recently, the heterostructure via integration of 2D material with nanophotonic waveguides is opening an avenue for many on‐chip applications of phosphorene. However, the thermo‐optic (TO) properties, which are widely used for waveguide heaters, are not studied on b‐AsP yet. Herein, the TO effects of a b‐AsP/silicon van der Waals heterostructure are first investigated and its application as a transparent waveguide heater is demonstrated. A high efficiency of 0.74 nm mW−1 is achieved with a nonresonant and broadband heater based on 20 nm thick b‐AsP, which eliminates the need for enhancement by cavity‐assisted light–matter interaction, and thus allows for compact footprint, broadband operation, and low latency. [ABSTRACT FROM AUTHOR]

In recent years, layered black phosphorus (BP) nanostructures have demonstrated great potential applications in transistors, optoelectronics and logic devices due to their excellent intrinsic electronic and optoelectronic properties. However, the high cost of BP and its rapid degradation upon exposure to ambient conditions turn out to be the two critical bottlenecks hampering practical applications. With the development of semiconductors in leaps and bounds, a new wave of exploration of black phosphorus analogues (BPAs), whose excellent optoelectronic performance and high chemical stability under ambient conditions unveil great promise for practical applications, has emerged. This review presents the synthesis and morphology control of emerging BPAs, the latest progress in understanding the fundamental properties of BPA nanostructures, and the recent advances in constructing prototypical high-performance BPA-based devices for practical applications. Finally, the prospects for future research, application opportunities, and the accompanying challenges of BPAs are discussed. [ABSTRACT FROM AUTHOR]

All-optical modulators fully manipulating one light by another light in the photonics domain have attracted great research interest in optical interconnects, optical communication networks etc. By employing an all-fiber Michelson interferometer, an all-optical phase and intensity modulator based on the excellent photothermal effect of few-layer bismuthene, for the first time, has been designed and successfully verified with multifunctional properties, including phase shifting, wavelength tuning, intensity modulating and information loading. Besides these multifunctional properties, it possesses a high conversion efficiency, excellent wavelength-tunable precision, large modulation depth and switchable output logic. We believe that this multifunctional all-optical modulator provides fundamental guidance on the design of all-optical systems with the fewest types of basic devices. It is therefore anticipated that this contribution will promote the development of two dimensional nanomaterial-based all-optical modulators towards all-optical communication and computing in the future. [ABSTRACT FROM AUTHOR]

It is widely known that excellent intrinsic electronic and optoelectronic advantages of black phosphorus (BP) make it attractive for applications in transistor, logic and optoelectronic devices. However, easy degradation upon exposure to ambient conditions turns out to be the most critical bottleneck in restricting its practical applications. In order to simultaneously achieve good stability and high device performance, a two-dimensional (2D) size-selected black-phosphorus-analogue (BPA), tin monosulfide nanosheets (SnS Ns), with enhanced chemical stability was successfully fabricated by a facile liquid phase exfoliation (LPE) method, followed by a liquid cascade centrifugation (LCC) technique. Similar to BP, SnS shows thickness modulated bandgap energy. The as-prepared SnS Ns were employed to fabricate working electrodes for photoelectrochemical (PEC)-type broadband photodetection for the first time, and they exhibit an appropriate capacity for a self-powered broadband photoresponse. More importantly, due to the weak polar character of Sn–S bonds, the SnS-based photodetector shows strong long-term temporal and cycling stability of ON/OFF switching behaviour without any external protection not only in regular basic electrolytes but also under strong polar conditions including harsh acidic and neutral electrolytes. We therefore anticipate that SnS as an emerging optoelectronic material might be developed towards versatile applications such as photodetection, sensing and modulation, etc. [ABSTRACT FROM AUTHOR]

Ternary copper antimony sulfide nanocrystals (CAS NCs), a promising solar cell candidate, have been proposed and investigated from the perspective of synthesis method, linear optical response, and size and band structure tunability. Herein, we present the intensity related nonlinear absorption using the Z-scan technique. Electron and hole relaxation dynamics for the as-prepared three phases, CuSbS2, Cu3SbS4 and Cu12Sb4S13 NCs, are studied at the visible spectrum band. With the assistance of fs-resolved transient absorption spectrum technology, photon induced charge carrier dynamics within the valence/conduction band and trap states are analyzed and attributed to three relaxation processes, the corresponding lifetimes of which are ∼400 fs, ∼5 ps and ∼60 ps, respectively. This analysis on electron and hole spatial separation and recombination is significant for the improvement of CAS NC based devices, and paves the way for the application of semiconductor NCs in photovoltaic devices, optical detection and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: All‐optical modulators, wherein signal light can be manipulated by another controlling light, have recently emerged as a promising perspective in all‐optical communications, interconnects and signal processing. Herein, by taking advantage of the strong light‐matter interaction and thickness‐dependent direct energy bandgap in few‐layer phosphorene, an all‐fiber all‐optical modulator based on a Mach–Zehnder interferometer comprising few‐layer fluorinated phosphorene‐deposited microfiber has been devised and further demonstrated with phase modulation ability. The phase shift of the signal light, capable of being converted into intensity modulation, could be readily controlled by the photothermal effect in phosphorene. A maximal phase shift of 8π is obtained at a control light of 290 mW, corresponding to a conversion efficiency of 0.029 π mW−1. The optical information carried by the control light is successfully copied towards the signal light with a modulation depth of 17 dB and a rise time constant of 2.5 ms. Stability under ambient conditions is enhanced significantly thanks to atomistic fluorination in phosphorene that can overcome drawbacks of easy oxidation of intrinsic phosphorene and maintain performance for a long term. This prototypical phosphorene‐based all‐optical phase modulator will have a great potential to be applied in all‐optical information processing and be integrated into optical fiber systems. [ABSTRACT FROM AUTHOR]