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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]

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]

[Display omitted] • This paper focuses on a novel analytical method based on packed-nanofibers solid-phase extraction coupled with HPLC-FLD to determine aflatoxins G1, B1, G2, B2 in foods, which contribute vitally to the application of nanoscience and material technology on the agricultural and food chemistry and analytical field. • This study confirmed that the as-synthesized electrospun nanofibers as adsorbent displays preferable potential practical application in the simultaneous pretreatment and analysis of toxins from various samples. • Under optimized conditions, one-step sample pretreatment integrating extraction, purification, enrichment and elution, was realized. The method can simultaneously process 12 samples within 5 min on a semi-automatic array SPE processor. A novel analytical method based on nanofiber-packed solid-phase extraction (PFSPE) combined with HPLC-FLD has been successfully developed and applied to determine aflatoxin B1, B2, G1, G2 in foods. In order to effectively adsorb analytes from complex food matrices, four types of nanofibers based on skeleton of polystyrene–polyvinyl pyrrolidone were prepared by electrospinning and applied as adsorbent to home-made solid-phase extraction device. The effects of type of nanofibers, pH of sample, type and concentration of salt ion, type of activation solvent, type and volume of eluent, amount of nanofibers, and extraction time on the adsorption/desorption were investigated and optimized. Under optimal conditions, the method showed satisfactory linear relationship, with limits of detection (LODs) of 0.07–0.17 ng g−1, intra-day and inter-day RSDs for spiked samples of 1.3–8.0 % and 1.9–5.8 %, and absolute recoveries in the range of 60.1–98.4 %. The results presented the great potential to be utilized to determine AFs in foodstuffs. [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]

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]

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]

All‐optical modulators, where one light modulates the parameters of another light (intensity, phase, frequency, etc.) without external electronic control, have drawn extraordinary attention in all‐optical information processing. In this contribution, by taking advantage of the two‐pass structure of Michelson interferometer and the strong photothermal conversion efficiency of MXene nanomaterials, an all‐optical modulator is demonstrated with a modulation depth of >27 dB, a free spectrum range of 16.8 nm and a pump‐induced phase shift slope of 0.043 π mW−1. Moreover, the all‐optical modulator is successfully employed to switch on/off the intensity of the signal light and load information from one channel to another with comparable response time and baudrate. It is believed that the MXene‐based all‐optical modulator will open a door to practical applications of 2D materials‐based all‐optical devices in all‐optical signal processing. [ABSTRACT FROM AUTHOR]

In article number 1800313, Han Zhang and co‐workers demonstrate an all‐optical, actively Q‐switched fiber laser enabled by an antimonene‐based all‐optical modulator. The pulsed pump light is absorbed by the 2D antimonene and induces intensity modulation of the signal light, causing the regulation of the intra‐cavity quality factor and the generation of Q‐switching pulses. [ABSTRACT FROM AUTHOR]

Q‐switched fiber lasers are of great interest in industrial material processing, nonlinear frequency conversion, spectroscopy etc. However, passive Q‐switching possesses drawbacks of degradation and failure of the saturable absorber and the difficulty in accurate modification of the repetition rate. To overcome these issues, active Q‐switching that can normally modulate the cavity quality‐factor by an externally‐driven Q‐switcher is in high demand. Herein, an actively Q‐switched laser with antimonene‐based all‐optical modulator is devised based on the high photo‐thermal efficiency (48%) and broadband response in antimonene. It is demonstrated that this actively modulated laser represents all‐optically tunable output parameters (e.g., output repetition rate), environmental stability, and easy synchronization. It is anticipated that this actively antimonene‐based all‐optical modulator with advantages of large modulation depth, low energy consumption, and high conversion efficiency has great potential in all‐optical information processing and pulsed laser engineering. An all‐optical, actively Q‐switched fiber laser enabled by an antimonene‐based all‐optical modulator is demonstrated by taking advantage of the high photo‐thermal efficiency and broadband response in antimonene. It is demonstrated that this actively modulated fiber laser represents all‐optically tunable output parameters, environmental stability, and easy synchronization, and has great potentials in information processing and pulsed laser. [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]

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]

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]

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]

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]

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]

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]

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]

• Comprehensive Review of GDY Saturable Absorber Application in Lasers. • Introduction to the Integration of GDY Saturable Absorber Devices. • Summarizing the Application of GDY in Optoelectronic Devices. • In-depth analysis of GDY's Synthesis and Third-order Nonlinear Characteristics. Graphdiyne (GDY) is a rising star among carbon allotropes, which represents the development trend and research direction of carbon materials in the field of ultrafast photonics. This review introduces the influence of GDY on optical and electronic properties, as well as the processing and integration strategies in saturable absorber (SA) devices, along with the research progress on third-order nonlinear optical properties. These GDY-SAs can serve as versatile, wideband ultrafast optical switches for ultrafast lasers. A comprehensive review of the current research status of pulsed lasers based on GDY-SAs demonstrates that GDY is a promising saturable absorber in ultrafast photonics applications. Finally, this review outlines the challenges and prospects faced by the future development of GDY-SAs, providing new potential efficacy for the application of GDY and its carbon family in ultrafast photonics technology. [ABSTRACT FROM AUTHOR]

As a new class of 2D materials, MXenes have attracted a lot of interest because of their prominent performance in versatile applications, such as batteries, supercapacitors, catalysts, electronics, and optics. In this work, an all‐optical modulator using MXene Ti3C2Tx deposited on a microfiber is proposed. By inserting an MXene‐deposited phase shifter into one arm of a Mach–Zehnder interferometer, the MXene Ti3C2Tx absorbs the control light and generates heat, which induces significant refractive index changes through strong light–matter interactions and thermo‐optic effects. In this study, a maximum phase shift of 16π is obtained, and an efficient all‐optical switch with an extinction ratio of more than 18.53 dB and a rise time constant of 4.10 ms are demonstrated. The advantages of this modulator include its all‐fiber content, low cost, ease of integration, and compactness. All‐optical modulators based on thermo‐optical effects will play an active role in the future of optical communications and optical information processing. [ABSTRACT FROM AUTHOR]

Tellurium (Te), as one of the rarest stable solid elements far more common in the universe than on earth, is a p‐type semiconductor with excellent optical properties. Herein, a novel two‐dimensional (2D) Te nanosheets (Ns)‐based air‐stable nonlinear photonic devices: all‐optical switcher and photonic diode, owing to its strong light–matter interaction in the visible‐to‐infrared band are reported. The findings validate that the proposed photonic diode can be utilized for the function of nonreciprocal light propagation in optical telecommunications or integrated photonics. Moreover, 2D Te‐based light‐modulate‐light system is successfully designed to realize "ON" and "OFF" modes for all‐optical switching operation. This work highlights a good promise of 2D Te in the field of nonlinear photonics, leading to an important step toward 2D Te‐based advanced photonics devices. The versatile solution process allows a universal access of 2D Te as a new 2D material in a wider range of photonics device applications such as, detector, modulator, switcher, etc. 2D tellurium, which has a strong nonlinear optical response, is demonstrated to have good application potential in nonlinear photonic devices. Herein, a novel 2D Te Ns‐based air‐stable nonlinear photonic device, all‐optical switcher and photonic diode, owing to its strong light–matter interaction in the visible‐to‐infrared band, is reported. [ABSTRACT FROM AUTHOR]

• The 'memory' ability in the relaxation oscillation state has disappeared in similariton fiber lasers due to the strong spectral filtering effect. • The build-up time is much shorter than the other fiber lasers mode-locked by the nonlinear polarization evolution. • The extinction process of the similariton fiber laser is observed and evaluated for the first time as well. • The spectral broadening and spectral 'breathing' process can be clearly observed in our experiment. Similaritons have attracted considerable attention thanks to their outstanding output performance in recent years. In this paper, we explored the entire dynamic evolution process of similaritons in an all-normal dispersion fiber laser through the time-stretch dispersive Fourier transform technique. Particularly, the narrow-band spectral filtering effect on the pulse evolution dynamics has been discovered. The "memory" ability in the relaxation oscillation state has disappeared in similariton fiber lasers compared with the traditional soliton mode-locked fiber lasers, and the build-up time is much shorter than other fiber lasers mode-locked by the nonlinear polarization evolution. Furthermore, the extinction process of the similariton fiber laser is observed and evaluated for the first time as well. An unstable time period accompanied by a high spectral peak over the spectrum is captured during the extinction process, and then the damped relaxation oscillation state is observed. These results can provide new perspectives into the ultrafast transient process of similaritons in all-normal dispersion fiber lasers and the dynamics of sophisticated nonlinear systems. [ABSTRACT FROM AUTHOR]

Serious nonradiative recombination and decomposition of perovskite film exist in MAPbBr3-based perovskite light-emitting diodes (PeLED) due to the residue of lead atoms from an incomplete reaction, thereby limiting the efficiency of PeLEDs. Excessive Methylammonium bromide (MABr) added into the precursor of methylammonium lead bromide (MAPbBr3) can solve this problem. However, how the excessive MABr self-passivates perovskite films improves the performance of PeLEDs requires further examination. The self-passivated perovskite film by overdoping MABr was investigated by varying stoichiometric ratios of perovskite precursors. It was found that, as the content of MABr increased, the interaction between free charge and longitudinal optical phonons was enhanced, thus reducing the exciton binding energy, resulting in emission broadening and blue shift of the PL spectra. With the molar ratio of PbBr2 and MABr of 1:1.315, the PeLED achieved a good trade-off between the brightness and the stability, thus demonstrating a maximum brightness of 9981 cd m − 2 and a lifetime of 14 min, with a maximum current efficiency of 6.59 cd A − 1. [ABSTRACT FROM AUTHOR]

Abstract: By solving the Haus master equation through split step Fourier transform method, several programs which can simulate the soliton mode-locked dynamic processes of the passively mode-locked solid laser with a semiconductor saturable absorber mirror (SESAM) are established, based on a MATLAB environment. The pulse evolution equations are solved numerically. Sample calculations for a diode-pumped Nd3+:YVO4 (0.5% doped) laser with a SESAM are presented to demonstrate the use of the simulation programs and the related formulas. Several theoretical results such as the pulse width, the peak power and the average output power are obtained with a given cavity structure, which are in good agreement with the reported experimental results. [Copyright &y& Elsevier]

• Bismuthene quantum dots (Bi-QDs) were fabricated by the LPE method. • Bi-QDs possessed large nonlinear optical properties in NIR region. • Bi-QDs SA Q-switched lasers can produce the minimum pulse duration of 150 ns. • Absorption cross sections of Bi-QDs were investigated for the first time. • The influence of trap state lifetime on the pulse generation was numerically simulated. Bismuthene quantum dots (Bi-QDs) were synthesized via the liquid phase exfoliation (LPE) method for the passive Q-switching operation in near-infrared (NIR) region. The nonlinear optical properties of the prepared Bi-QDs were investigated by the open-aperture Z-scan technology. The modulation depths were 18.1% and 5.1% at 1.06 and 1.34 µm, respectively. Based on the Bi-QDs saturable absorber, passively Q-switched Nd:GdVO 4 lasers operating at 4F 3/2 → 2I 11/2 and 4F 3/2 → 2I 13/2 transitions were demonstrated, showing the wideband optical modulation in NIR regime. For the 4F 3/2 → 2I 13/2 transition lasing at 1.34 µm, the shortest pulse duration of 155 ns was obtained with a repetition rate of 457 kHz. With respect to the 4F 3/2 → 2I 11/2 transition at 1.06 µm, the minimum pulse duration was 150 ns with a repetition rate of 424 kHz, leading to a single pulse energy of 261 nJ and a peak power of 1.68 W. In addition, the ground state absorption cross section and the excited state absorption cross section of Bi-QDs were also investigated for the first time. The impact of the excited state lifetime on the output parameters was numerically stimulated by the coupled rate equations. Our work confirmed that the trap state in Bi-QDs played an important role in the pulse generation mechanism. [ABSTRACT FROM AUTHOR]

Optical signal processing based on 2D materials is a hot topic which has attracted rising interests. As a novel class of 2D material, MXene is becoming a promising nonlinear photonics material. In this contribution, MXene Ti3C2Tx, prepared by liquid acid etching method, is developed as a novel all‐optical device by depositing on a microfiber, which shows an excellent nonlinear optical response at the telecommunication band. The as‐fabricated device is employed as a wavelength converter based on the nonlinear four‐wave mixing effect with a conversion efficiency of –59 dB carrying a 10 GHz signal. The proposed all‐optical wavelength converter based on MXene Ti3C2Tx can play a remarkable role in the future of optical communications and optical information processing. [ABSTRACT FROM AUTHOR]

A new member of the IV–V compounds, germanium–phosphorus (Ge–P) compounds, has been shown in experiment and theory to have a tunable bandgap (Eg), excellent chemical stability, strong in‐plane anisotropy, and wide‐range optical absorption, all indicating a promising future in electronic and optoelectronic applications. In this work, the application potential of Ge–P compounds as nonlinear optical (NLO) materials in ultrafast photonics is studied for the first time. The strong light–matter interaction, broad and tunable Ep, and broadband and strong optical response make GeP a likely NLO material for photonics, especially in infrared photonic devices. In addition, 2D GeP nanosheets are mixed with poly(vinylidene fluoride) (PVDF) to obtain a GeP@PVDF composite film, which further improves the stability of the GeP and, for the development of organic photonic devices, helps to slow its degradation. From Z‐scan data and fitting results, it is found that GeP has an excellent broadband NLO response. Moreover, using the GeP@PVDF composite film as a saturable absorber, a high‐stability femtosecond laser with a 722 fs pulse width is obtained in the telecommunications band. Preliminarily, Ge–P compounds display excellent optical properties suggesting that they may be used as NLO materials in advanced photonic devices. [ABSTRACT FROM AUTHOR]

In article number 1800215, Shunbin Lu, Shixiang Xu, Han Zhang, and co‐workers demonstrate that two‐dimensional MXene exhibits strong nonlinear optical response at the visible‐light region due to the optical Kerr effect. When the laser beam passes through the MXene, the diffraction rings can be excited with spatial self‐phase modulation techniques. Moreover, the MXene is developed as the information converter to realize the modulation of pump light to probe light in an all‐optical switcher/modulator. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) Ti3C2Tx (T = F, O, or OH) MXene, a graphene‐like material, is successfully fabricated for an investigation in nonlinear optics. Its nonlinear refractive index (n2 ≈ 10−4 [cm2 W−1]) and third‐order nonlinear susceptibility (χ monolayer (3)≈ 10−7 [e.s.u.]) are experimentally confirmed by spatial self‐phase modulation (SSPM) techniques. Applying its strong Kerr effect, a novel all‐optical switcher based on 2D MXene is designed to realize the modulation of pump light to probe light. This indicates that MXene could act as an information converter in an optical light‐control‐light system. Meanwhile, probe light is induced by the pump light to excite diffraction rings, and the ring numbers of the probe light can be controlled to increase by the regulation of the other pump light. Through modulation of the pump light, the "ON" and "OFF" modes in the all‐optical switcher/modulator can be achieved. This work highlights the potential of Ti3C2Tx MXene materials applied in all‐optical switcher/modulators, which can be considered an important step toward MXene‐based advanced photonics devices. The nonlinear optical response of 2D Ti3C2Tx (T = F, O, or OH) MXene is investigated with spatial self‐phase modulation techniques for application in advanced photonics devices. Through modulation of the pump light, the "ON" and "OFF" modes in the MXene‐based all‐optical switcher/modulator are achieved. [ABSTRACT FROM AUTHOR]