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Benefitting from the excellent characteristics such as low cytotoxicity, functionalization versatility, and tunable fluorescence, nanodiamonds (NDs) have shown enormous application potentials in the biomedical field. Herein, we proposed, for the first time to our best knowledge, to integrate NDs on a plasmonic interface constructed on a side-polished fiber using drop-casting method. The added NDs engineers the plasmonic interface towards improving the sensing field, thus enhancing the sensitivity, which, moreover, is significantly dependent on the number of drop-casting cycles (DCs) and the used concentration of NDs dispersion solution. Experimental results suggest that properly increasing the NDs dispersion concentration is beneficial to obtain a higher sensitivity while using a fewer number of DCs, but the excessive concentration extremely deteriorates the resonance dip. Experimentally, using the optimal 0.2 mg/mL concentration and 3 DCs, we achieve the highest RI sensitivity of 3582 nm/RIU, which shows an enhancement of 73.8% compared to the case without NDs modification. The sensitivity enhancement in biosensing is also proved by employing bovine serum albumin as a demo. The behind mechanism is explored via characterizations and simulations. This work opens up a new application form for NDs, i.e. integrating NDs with a plasmonic interface towards high-performance biosensing.

With the rising need for energy resources, considerable work has done for building novel energy storage technologies. Supercapacitors (SCs) and batteries are a highly competitive choice for electrochemical energy storage devices (EESDs) due to their ultrahigh power density, improved rate capability, long-term cyclability, and remarkable safety. Because of their novel properties such as high mechanical flexibility, large specific surface area (SSA), chemical stability, and superior electric and thermal conductivities, graphene-based nanomaterials (NMs) have attracted considerable attention as alternative electrode materials for EESDs. Graphene is gaining a lot of interest since it has amazing qualities including 230 000 cm2 V-1 s-1 charge mobility, 3000 W m-1 K-1 thermal conductivity, 2.3% visible light absorption, 130 GPa mechanical strength, and 2600 m2 g-1 specific surface area (SSA). Mechanical exfoliation, reduction of graphene-oxide, chemical vapor deposition (CVD), and epitaxial growth of graphene-NMs are some of the synthetic procedures that can change these characteristics. Despite much effort, the detailed screening of high-performance electrode materials, such as graphene-based NMs, is still necessary. We covered the recent advancements in graphene-based NM research and development for high-performance batteries and SCs for specific applications in the next generation and smart electronics in this study. First, we discuss rechargeable batteries, a new-concept based on graphene with high energy density, longer life, improved safety, and shape-diversity capabilities in order to meet the needs of future electronics. Second, we discuss SCs for the present advanced nanotechnologies that outperform batteries with respect to power density, cyclability, quick charging/discharging rates capability, straightforward principles, high activity of the charge circulation, and low maintenance expenditure, including electrical double layer capacitors (EDLCs) and pseudocapacitors (PCs). Finally, graphene-based electrodes used in ESDs with their prospects and problems are briefly reviewed.

As the critical device of microwave photonics and optical communication, the low-loss and high-efficiency optical phase shifter has attracted intense attention in photonic integrated circuits. However, most of their applications are restricted to a particular band. Little is known about the characteristics of broadband. In this paper, an SiN-MoS2 integrated broadband racetrack phase shifter is demonstrated. The coupling region and the structure of the racetrack resonator are elaborately designed to improve the coupling efficiency at each resonance wavelength. The ionic liquid is introduced to form a capacitor structure. Then, the effective index of the hybrid waveguide can be efficiently tuned by adjusting the bias voltage. We achieve a phase shifter with a tunable range covering all the WDM bands and even up to 1900 nm. The highest phase tuning efficiency is measured to be 72.75 pm/V at 1860 nm, and the corresponding half-wave-voltage-length product is calculated as 0.0608 V·cm.

Ultrafast fiber lasers with a wide spectral range have huge demands for many applications. In this article, magnetron sputtering deposition (MSD) technique was utilized to prepare a new broadband microfiber based Sb thin film saturable absorber (SA), and ultrafast pulses in both 1.5 and 2 μm wavebands were generated with the integrated microfiber-based Sb thin film SA in erbium-doped fiber laser (EDFL) and thulium-doped fiber laser (TDFL), respectively. Pulse duration of 544 fs/972 fs and output power of 21.76 mW/36.1 mW centered at 1557 nm/1892 nm were respectively produced from stable mode-locked EDFL and TDFL. To the best our knowledge, this is the first time that ultrafast fiber lasers including both 1.5 μm and 2 μm wavebands were mode locked by a single microfiber-based Sb thin film SA.

We demonstrate a low-power, compact micro-ring phase shifter based on hybrid integration with atomically thin two-dimensional layered materials, and experimentally establish a low-loss silicon nitride platform. Using a wet transfer method, a large-area few-layer MoS

Graphdiyne (GDY), which possess sp- and sp2-hybridized carbon and Dirac cones, offers unique physical and chemical properties, including an adjustable intrinsic bandgap, excellent charge carrier transfer efficiency, and superior conductivity compared to other carbon allotropes. These exceptional qualities of GDY and its derivatives have been successfully used in a variety of fields, including catalysis, energy, environmental protection, and biological applications. Herein, we focus on the potential application of GDY and its derivatives in the biomedical domain, including biosensing, biological protection, cancer therapy, and antibacterial agents, demonstrating how the biomimetic behavior of these materials can be a step forward in bridging the gap between nature and applications. Considering the excellent biocompatibility, solubility and selectivity of GDY and its derived materials, they have shown great potential as biosensing and bio-imaging materials. The unusual combination of properties in GDY has been used in biological applications such as “OFF–ON” DNA detection and enzymatic sensing, where GDY has a greater adsorption capacity than graphene and other 2D materials, resulting in increased sensitivity. GDY and its derivatives have also been used in cancer treatment due to their high doxorubicin (DOX) loading capacity (using-stacking) and photothermal conversion ability, and radiation protection since their initial biological use. The poor biodegradation rate of graphene demands the search for new nanomaterials. Accordingly, GDY has better biocompatibility and bio-safety than other 2D nanomaterials, especially graphene and its oxide, due to its absence of aggregation in the physiological environment. Thus, GDY-based nanomaterials have become promising candidates as bio-delivery carriers. Besides, GDY and GDY-based materials have also shown interesting applications in the fields of cell-culture, cell-growth and tissue engineering. Herein, we present a comprehensive review on the applications of GDY and its derivatives as biomedical materials, followed by their future perspectives. This review will provide an outlook for the application of graphene and its derivatives and may open up new horizons to inspire broader interests across various disciplines. Finally, the future prospects for GDY-based materials are examined for their potential biological use.

A strong electrocatalytic activity of the MXenes nanomaterials (NMs) has gained a lot of concentration as cutting edge materials in a variety of electrocatalytic devices in a broad range of industrial uses. In recent years, the production and utilization of the MXenes NMs as an electrocatalysts has progressed, with more than 50 distinct variants found and used. We reviewed and discussed in this article the latest detail progress in the synthesis, selected properties and potential applications of the MXenes as an electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting, oxygen reduction reaction (ORR), nitrogen reduction reaction (N2RR), CO2 reduction reaction (CO2RR) etc. We will also discuss the numerous approaches for increasing MXenes electrocatalytic activity for target products. At the end, we will also talk about the present obstacles and future suggestions for the MXenes as HER, ORR, OER, NO2RR and CO2RR electrocatalysts.

A passively mode-locked thulium-doped fiber laser using a tungsten ditelluride saturable absorber ( W T e 2 - S A ) is demonstrated. High-power mode-locked pulses with an average output power of 108.1 mW were achieved by incorporating the W T e 2 - S A into a thulium-doped fiber oscillator. To the best of our knowledge, this is the highest average power obtained from a W T e 2 - S A -based fiber laser. We further amplified the output power to 5.60 W with an all-fiber thulium-doped double-cladding fiber amplifier. Our result indicates that W T e 2 - S A could be an excellent candidate for a high-power fiber laser system.

We demonstrate the HfSe

A monolayer of black phosphorus (BP), commonly known as phosphorene is a novel member of the two-dimensional (2D) materials family. In consequence of its “puckered” lattice structure, phosphorene has a larger surface to volume ratio than graphene and transition metal dichalcogenides (TMDCs), and has revealed some distinct benefits in sensing applications. Since, its first synthesis in 2014 by mechanical exfoliation has spurred a wave of material science research activity. Phosphorene's structure and anisotropic characteristics, with its applications in transistors, batteries, solar cells, disease theranostics and sensing has been the subject of several reviews. This pursuit has sparked a flurry of new areas of research, theoretical and experimental, targeted at technological breakthroughs. The target of this review is to explain current advances in phosphorene synthesis, properties, and sensing applications, such as gas sensing, humidity sensing, photo-detection, bio-sensing, and ion-sensing. Finally, we will discuss the present obstacles and potential for phosphorene synthesis, properties and sensing applications.

We demonstrate a low-power, compact micro-ring phase shifter based on hybrid integration with atomically thin two-dimensional layered materials, and experimentally establish a low-loss silicon nitride platform. Using a wet transfer method, a large-area few-layer MoS2 film is hybrid integrated with a micro-ring phase shifter, leading to a tuning efficiency of 5.8 pm V−1 at a center wavelength of 1545.294 nm and a half-wave-voltage-length product as low as 0.09 V cm. Our device is designed to provide a hybrid-integration-based active phase modulation scheme for integrated optical communication networks with large-cross-section silicon nitride waveguides.

In this letter, molybdenum ditelluride (MoTe2), a new member of the transition metal dichalcogenides family, has been characterized and fabricated as an optical modulator for the development of broadband wavelength tunable laser using a Tm3+-doped CaYAlO4 crystal as a laser gain medium. The maximum average output power reaches 0.75 W with the shortest pulse width of about $0.69~\mu \text{s}$ and repetition rate of 70.9 kHz, which leads to a pulse energy of about $10.58~\mu \text{J}$ and peak power of 15.3 W. Keeping the MoTe2 optical modulator inside the laser resonator and at the same time introducing an undoped YAG for wavelength tuning, wavelength tunable passively Q-switched laser operation with a wavelength range of about 112 nm has been demonstrated. This letter experimentally verifies the potential of the novel 2D material MoTe2 as an optical modulator. At the same time, this letter paves the way toward the realizations of simple and compact wavelength tunable pulsed laser sources based on broadband 2D materials saturable absorbers.

We have experimentally demonstrated both 1.82 μm and 1.84 μm Tm:YAP lasers at the operation mode of continuous-wave (CW) and mode-locking. These individual wavelength lasers are realized by using well-chosen output couplers. For the CW operation, a short Fabry-Perot cavity is employed. The maximum output power of the 1825 nm Tm:YAP laser is 7.04 W, and the corresponding slope efficiency is 59.3%. For 1844 nm Tm:YAP laser, the output power is 7.1 W. A commercial semiconductor saturable absorber mirror (SESAM) is used for realizing continuous-wave mode-locking (CWML) operation. The average output power of Tm:YAP laser at 1823.7 nm is 0.3 W, and the pulse duration is 126 ps. Further, stable CWML laser operating at 1844 nm is realized by inserting a 5 mm fused-quartz plate into the cavity with the Brewster angle. The average output power of 0.63 W is achieved, and the pulse duration is 156 ps.

Recently, the active controlled broadband terahertz (THz) emitter from semiconductor crystal has attracted considerable attention due to its field intensity tuning properties, which makes it a promising candidate for wide applications in THz photonics. A broadband THz wave radiation intensity by applying electric field control in an n-type semiconductor tin selenide (SnSe2) crystal had been reported. In addition, due to the weak phonon absorption of the material in the THz band, the resulting THz spectral range is up to 3.5 THz. With an applied voltage of −5 V, the actively modulated depth of THz intensity is up to 123%. Our work directly demonstrates that when the excited laser photon energy exceeds the material bandgap, photon drag effect would be the main mechanism of THz wave radiation rather than nonlinear effects. Owing to simple structure and high modulation depth, electrically controlled THz radiation, the SnSe2 crystal has great applications in generation and modulation devices in THz region.

We demonstrate a simple Fe3O4 nanoparticles (FONPs) based Q-switched fiber laser that is able to generate stable nanosecond pulses with single-wavelength or multiwavelength regimes. In the single-wavelength lasing scheme, the fiber laser generates 613-ns pulse with average output power of 41.2 mW, pulse energy of 321.3 nJ, and signal-noise-ratio of 54.4 dB. In the multiwavelength lasing scheme, stable pulse is achieved with 18-wavelength channels contained within the 3-dB bandwidth range. Our results prove that the FONPs can act as an effective Q-switch for high-energy pulse generation.

We demonstrate a compact all-fiber-optic vector magnetometer based on Mach-Zehnder interferometer by utilizing nano-magnetic fluid filled double-clad photonic crystal fiber (DC-PCF). The magnetic fluid (MF) serving as sensing elements is injected into the micro-channel-arrays of DC-PCF. The magnetometer is constructed by splicing a section of MF-filled DC-PCF between two standard single mode fibers forming a high stable all-fiber structure without any additional sealed capillary. The vector magnetometer has the capability of simultaneous measurement of magnetic field intensity and orientation by monitoring a specific dip wavelength shift or transmission loss of Mach-Zehnder interference spectrum. The magnetometer with response sensitivities of 114.5 pm/mT, 1.79 dB/mT (X-axis) and 41.9 pm/mT, 0.52 dB/mT (Y-axis) at two particular orthogonal magnetic field orientations was fabricated and investigated.

Vanadium Diselenide (VSe 2 ) has a high electrical conductivity owing to the electron delocalization of the vanadium lattice framework. Most of previous research has been focused on its electronic properties. The nonlinear optical properties of VSe 2 have not been investigated yet. Herein, we prepared few-layer VSe 2 nanoflakes by liquid phase exfoliation. Subsequently, we utilized Z-scan technique to study the nonlinear optical properties of few-layer VSe 2 nanoflakes. And we prepared VSe 2 based saturable absorbers (SA) and achieved passively mode-locked operation in Er-doped fiber laser. The results indicate that VSe 2 nanosheets own remarkable nonlinear optical properties and could be employed as ideal saturable absorption materials in pulsed fiber lasers.

Single crystalline titanium dioxide thin film in the rutile phase (r-TiO2) is exfoliated from bulk material using a He+-implantation method, and is bonded onto SiO2 substrate to form a heterostructure using Cu-Sn bonding technology. The exfoliated r-TiO2 thin film was examined to be in good quality, and the exfoliation mechanism of ion-implanted r-TiO2 was analyzed. The obtained r-TiO2 thin film heterostructure with high refractive index contrast has a potential application in the fabrication of high-Q optical microcavities in visible wavelengths, which is useful in integrated photonic devices.

As one of the greatest inventions in the 20th century, ultrafast lasers have offered new opportunities in the areas of basic scientific research and industrial manufacturing. Optical modulators are of great importance in ultrafast lasers, which directly affect the output laser performances. Over the past decades, significant efforts have been made in the development of compact, controllable, repeatable, as well as integratable optical modulators (i.e., saturable absorbers). In this paper, we review the fundamentals of the most widely studied saturable absorbers, including semiconductor saturable absorber mirrors and low-dimensional nanomaterials. Then, different fabrication technologies for saturable absorbers and their ultrafast laser applications in a wide wavelength range are illustrated. Furthermore, challenges and perspectives for the future development of saturable absorbers are discussed and presented. The development of ultrafast lasers together with the continuous exploration of reliable saturable absorbers will open up new directions for the mass production of the next-generation optoelectronic devices.

We demonstrated a novel ultracompact fiber-optic micro-Michelson interferometer (MMI) for high temperature sensing. In the MMI structure, a 45° angled reflector is polished at the tip of a single mode fiber using a fiber-lensing machine. This reflector divides the fiber core into two parts and splits the inputting light into two beams producing Michelson interference fringe. The experimental results indicate that the proposed sensor has average temperature sensitivity of 13.32 pm/°C as the temperature increases from 19 °C to 950 °C. With the all-glass assembly-free-based structure, the sensor has a capability of surviving in the high temperature harsh environment.

A position determination method for low-coherence interference fringe in optical fiber sensing is proposed. This method can be used to measure displacement or length. An amplitude ratio curve is created from spatially modulated interference fringes. There is a one-to-one correspondence relationship between the peaks of the amplitude ratio curve and the extremes of the low-coherence interference fringe. The peak positions of the amplitude ratio curve only rely on the Fabry-Pérot (F-P) cavity length. In addition, the peaks of the amplitude ratio curve are very sharp, which can be easily identified. In the calculation of the amplitude ratio curve, the low-coherence interference fringe is spatially modulated by Pockels effects. The impacts of the modulated voltage on the sensing precision are analytically and numerically discussed. Compared with the envelop detection method, the position determination precision of low-coherence interference fringe is enhanced about 30 times by creating an amplitude ratio curve. This method can be widely employed in the sensing of all kinds of parameters that can be converted to displacement or length.

We demonstrate a compact in-fiber integrated microresonator based on a silica microsphere and microstructure fiber. Whispering-gallery-modes (WGMs) are effectively excited through evanescent field coupling between the silica microsphere and one of the input tube waveguides of negative curvature fiber. The WGM spectrum with the Q-factor of ∼2.56 × 103 and the extinction ratio of ∼15.2 dB is achieved. The transmission spectra evolution for 5 h reveals the long-term stability of WGM excitation. The experimental results indicate that the in-fiber integrated resonator has the advantages of high stability, high integration, robustness, alignment-free assembly structure, and low cost, motivating potential applications in the lab-in-fiber platform.

We demonstrate the HfSe2 saturable absorber (SA) for the generation of ultrafast pulse laser. The HfSe2 SA device is fabricated by integrating HfSe2 nanosheets (NSs) with a microfiber. The material and optical characteristics of HfSe2 NSs show their high quality. The nonlinear optical absorption of HfSe2 SA is measured with a modulation depth of 5.8%. Stable soliton mode-locked laser based on HfSe2 SA is realized at the central wavelength of 1561.43 nm with pulse duration of 297 fs and the maximum pulse energy of 2.68 nJ. Our soliton fiber laser has a maximum output power of 48.5 mW with a high slope efficiency of 12.8%, which indicate that HfSe2 is a good candidate of SA for high efficient ultrashort pulses generation.

Two-dimensional layered materials have been widely utilized as nonlinear absorption materials to transfer continue-wave into pulse trains in fiber laser systems. Here, we prepare robust GaSe/GeSe composites with high power bearing capacity as saturable absorbers (SAs) and then investigate their nonlinear optical properties via broadband Z-scan measurement at 800 nm and 1550 nm, respectively. The modulation depths of GaSe/GeSe based SAs are measured to be 11.97% and 7.69% at 1550 nm. After incorporating the GaSe/GeSe SAs into an Erbium-doped fiber laser cavity, passively Q-switched pulse trains could be obtained with repetition rates changing from 83.58 to 136.78 kHz (70.41 to 161.65 kHz). The maximum output power and pulse energy are 52.1 mW/370.67 nJ (GaSe) and 21.6 mW/133.74 nJ (GeSe) under the maximum pump power of 600 mW. The results indicate that GaSe and GeSe possess outstanding thermal stability and could be employed as remarkable saturable absorption materials for high-energy pulses generation.

A passively mode-locked thulium-doped fiber (TDF) laser was realized by employing chemical vapor deposited few-layer molybdenum ditelluride (MoTe2) as a saturable absorber (SA). The few-layer MoTe2 film was transferred onto the waist of a microfiber and then incorporated into a TDF laser with a typical all-fiber ring cavity configuration. Stable soliton pulses emitting at 1930.22 nm were obtained with a 3 dB bandwidth of 4.45 nm, a pulse duration of 952 fs, and an average power of 36.7 mW.

Two-dimensional materials have become the focus of research for their photoelectric properties, and are employed as saturable absorption materials. Currently, the challenge is how to further improve the modulation depth of saturable absorbers (SAs) based on two-dimensional materials. In this paper, three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method. The nonlinear optical responses of the WSe2 films including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments. Different modulation depths are successfully obtained by controlling the thickness of the WSe2 films. We further incorporate them into an all-fiber laser to generate mode-locked pulses. The mode-locked fiber lasers with a pulse duration of 185 fs, 205.7 fs and 230.3 fs are demonstrated when the thickness of the WSe2 films is measured to be 1.5 nm, 5.7 nm and 11 nm, respectively. This work provides new prospects for WSe2 in ultrafast photonic device applications.

We prepared ReS 2 nanosheets by liquid-phase exfoliation and fabricated ReS 2 saturable absorbers with all-fiber integrated structure. Their nonlinear optical properties were investigated systematically. The results demonstrate that ReS 2 nanosheets owns excellent nonlinear saturable absorption properties.

A high precision demodulation method in frequency domain is proposed for a polarized low-coherence interferometer with location-dependent birefringence dispersion. By minimizing the frequency nonlinearity caused by dispersion effects, the proposed method avoids the jump errors of traditional frequency domain analysis method and exactly retrieve the absolute phase at multiselected-wavenumber point simultaneously, which makes it superior in accuracy, stability, and measurement range. We carried out experiments with an optical fiber Fabry–Perot pressure sensing system to verify the effectiveness of the proposed method. The experiment result showed that the measured error was less than 0.049 kPa and the measurement range was widened to 285 kPa, which could be wider with suited experimental equipment and is no limit in theory.

We establish an optical path difference (OPD) distribution model in a spatial scanned polarized low-coherence interferometry (LCI) considering the nonperpendicular incidence of light to explore the spatial frequency drift. Simulation shows that the OPD is no longer linearly distributed on a charged coupled device (CCD) and that the spatial frequency drifts approximately linearly as low coherent interference fringe (LCIF) shifts. A compensation process for spatial frequency domain analysis (SFDA)-based algorithm is proposed to avoid interference-order misidentification and consequent jump error. We verified our analysis and effectiveness of the proposed algorithm with an optical fiber Fabry-Pérot pressure sensing experiment. The measured spatial frequency drift agreed well with simulation results, and the interference-order misidentification was eliminated.

We demonstrated a fiber-optic sensor using spheroidal-cavity-overlapped fiber Bragg grating (FBG) for simultaneous temperature and strain sensing. The spheroidal cavity is fabricated through splicing two sections of the photon-sensitive fiber together and located in the center of the FBG to act as a Fabry-Pérot interferometer (FPI). Experimental results demonstrate that the temperature sensitivity of the FPI part of the sensor is 0.67 pm/°C at the range of -70 °C-20 °C, and its strain sensitivity is 3.76 pm/με at the range of 0-500 με, while those of the FBG part are 8.40 pm/°C and 1.40 pm/με, respectively. The sensitivity difference ensures good simultaneous measurement performance.

Large-area and highly crystalline transition metal dichalcogenides (TMDs) films possess superior saturable absorption compared to the TMDs nanosheet counterparts, which make them more suitable as excellent saturable absorbers (SA) for ultrafast laser technology. Thus far, the nonlinear optical properties of large-scale WSe

Large-area and highly crystalline transition metal dichalcogenides (TMDs) films possess superior saturable absorption compared to the TMDs nanosheet counterparts, which make them more suitable as excellent saturable absorbers (SA) for ultrafast laser technology. Thus far, the nonlinear optical properties of large-scale WSe2 and its applications in ultrafast photonics have not yet been fully investigated. In this work, the saturable absorption of chemical vapor deposition (CVD) grown WSe2 films with large-scale and high quality are studied and the use of WSe2 films as a broadband SA for passively mode-locked fiber lasers at both 1.5 and 2 μm ranges is demonstrated. To enhance the light-material interaction, large-area WSe2 film is tightly transferred onto the side wall of a microfiber to form a hybrid structure, which realizes strong evanescent wave interaction between light and WSe2 film. The integrated microfiber-WSe2 device shows a large modulation depth of 54.5%. Using the large-area WSe2 as a mode-locker,stable soliton mode-locked pulse generation is achieved and the pulse durations of 477 fs (at 1.5 μm) and 1.18 ps (at 2.0 μm) are demonstrated, which suggests that the large-area and highly crystalline WSe2 films afford an excellent broadband SA for ultrafast photonic applications.

Transition metal dichalcogenides (TMDs) have been successfully used as broadband optical modulator materials for pulsed fiber laser systems. However, the nonlinear optical absorptions of exfoliated TMDs are strongly limited by their nanoflakes morphology with uncontrollable lateral size and thickness. In this work, we provide an effective method to fully explore the nonlinear optical properties of MoSe

Nanoferrofluid is emerging as promising nanomaterials for the critical element of magneto-optical fiber devices. Herein, we demonstrate the mechanism of anisotropic nanochain-clusters formation and motion of nanoferrofluid around an optical fiber with the variation of magnetic field intensity and its direction. Based on anisotropic distribution of nanochain-clusters, we design a new nanoferrofluid-based vector magnetometer with simultaneous measurement of magnetic field intensity and direction. The sensing mechanism is based on the tunable ERI modulation of asymmetric cladding modes in fiber, modulated by magnetic field dependent nanochain-clusters. The all-fiber vector magnetometer with direction detection error of ±1.5°, and intensity sensitivity of 222.0pm/mT was fabricated and investigated.

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted significant interest in various optoelectronic applications due to their excellent nonlinear optical properties. One of the most important applications of TMDs is to be employed as an extraordinary optical modulation material (e.g., the saturable absorber (SA)) in ultrafast photonics. The main challenge arises while embedding TMDs into fiber laser systems to generate ultrafast pulse trains and thus constraints their practical applications. Herein, few-layered WS2 with a large-area was directly transferred on the facet of the pigtail and acted as a SA for erbium-doped fiber laser (EDFL) systems. In our study, WS2 SA exhibited remarkable nonlinear optical properties (e.g., modulation depth of 15.1% and saturable intensity of 157.6 MW cm(-2)) and was used for ultrafast pulse generation. The soliton pulses with remarkable performances (e.g., ultrashort pulse duration of 1.49 ps, high stability of 71.8 dB, and large pulse average output power of 62.5 mW) could be obtained in a telecommunication band. To the best of our knowledge, the average output power of the mode-locked pulse trains is the highest by employing TMD materials in fiber laser systems. These results indicate that atomically large-area WS2 could be used as excellent optical modulation materials in ultrafast photonics.

We demonstrated a simple and batch-producible fiber-optic sensor based on hybrid Fabry-Perot (FP) configuration for simultaneous pressure and temperature sensing. The proposed sensor head chips are batch fabricated by double-sided anodic bonding of a through-holes-array-structured glass wafer and two silicon wafers. The silicon-glass-silicon sandwich bonding structure constructs two serially connected low-finesse FP cavities naturally. The first cavity (FP 1 ) is a silicon cavity and utilizes the refractive indices temperature dependence of silicon to achieve temperature sensing. The second cavity (FP 2 ) is a vacuum cavity and employs a thin silicon diaphragm as a pressure sensing element. The reflection spectra exhibit hybrid interference fringes with different frequencies produced by silicon and vacuum cavity, and the temperature and pressure are simultaneously measured. Experiment results demonstrate that the pressure sensitivity of FP 2 is 12.82 nm/kPa with a high linear pressure response over the range of 10-250 kPa, and the temperature sensitivity of FP 1 is 142.02 nm/°C under the range of -20 °C-70 °C.

We propose a direct and nondestructive self-referenced residual pressure measurement method for MEMS chip of fiber-optic pressure sensor. In the proposed method, two multimode fibers are placed at the center and the edge position of the sealed cavity. With scanning external pressure, two groups of cavity lengths data are obtained by using polarization low-coherence interference demodulator. The intersection point of their linear fitting curves indicates that the diaphragm is in flat condition and residual pressure is determined by the external pressure at this point. We successfully demonstrated the effectiveness of the residual pressure measurement method with measure error 0.049 kPa.

Despite extensive applications ranging from optoelectronic devices to flexible devices, two-dimensional layered materials used as ultrafast optical modulation materials have suffered from limited operation wavebands due to their intrinsic bandgap. Here, we investigate the nonlinear optical (NLO) response of group IIIA/IVA monochalcogenides XTe (X = Ga and Ge), which exhibit a remarkable saturable absorption response at a broadband wavelength. By using a liquid phase exfoliation technique, we prepare XTe nanosheets with few-layer thickness in a deionized water solvent and investigate their NLO responses at 800 nm, 1.5 µm, and 2 µm, respectively. Both GaTe and GeTe nanosheets exhibit ultrafast saturable absorption at 800 nm with 32.4 μJ (48.4 µJ) incident intensity. After preparing microfiber-based nanosheet optical modulators, their saturable absorptions are measured at 1.5 µm and 2 µm. The GaTe-SA possesses a little bit higher modulation depth (42.3% at 1.5 µm/30.7% at 2 µm) than the GeTe-SA (30.5% at 1.5 µm/8.3% at 2 µm) at two wavelengths. The lifetime of GaTe and GeTe nanosheets is measured to be 2.8 ps and 3.3 ps, respectively. In addition, we further examine their saturable absorption via incorporating them into an erbium- and a thulium-doped fiber laser system and obtain stably passively mode-locked pulse trains, respectively. The distinct NLO properties indicate a large potential of XTe nanosheets in the development of an ultrafast optical mode locker with a wideband operation wavelength.