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Due to the slowdown of Moore's law, the integrated photonic devices have provided a route to promote the development of large‐scale optical communications with high performance. As one of the essential components of optical routers, an optical switch can fast transmit or block the optical signal. However, most of the integrated optical switches reported to date rely on thermo‐, magneto‐, or electro‐optical effects, which limit applications due to slow response times, large footprint, and complexity fabrication. Here, an integrated nonlinear optical switch designed by the inverse‐design method and fabricated on the SiN platform is introduced. The integrated optical switch is demonstrated with significant intensity‐dependent transmission at 1.5 µm waveband. The polarization‐depended capability is explored by using fundamental polarized lights (transverse electric and transverse magnetic, respectively), which exhibits opposite transmission change trends during the whole power range and opens potential applications such as photonic quantum information processing. In order to address the saturation of Kerr‐nonlinearity in SiN materials at high power, a MoS2/SiN hybrid integrated optical switch is fabricated by uniformly cladding few‐layer MoS2 on the surface of inverse‐designed region. That is demonstrated to enhance the nonlinear optical response of device efficiently and achieve more excellent switching capability at high power. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Integrated photonics are expected to replace the conventional free‐space optical systems, yet there remains a challenge of low nonlinear response due to small nonlinear refractive index and short interaction length. Here, the large‐area monolayer MoS2 is used to facilitate excellent nonlinear response, and a pump strategy is proposed with respect to the spontaneous four‐wave mixing in the visible spectral range. The external pump incident from the top resonates in the GaN microdisk resonator and is thoroughly absorbed by the monolayer MoS2 to generate the four‐wave mixing pump via the excitonic photoluminescence. Being driven by the internal photoluminescence pump and enhanced by the microcavity structure, it is validated that the proposed structure well suffices efficient degenerate spontaneous four‐wave mixing generation. Since the emission spectrum can be tailored through careful temperature control, this work holds a great potential in various functionalities, not only on‐chip visible light sources but also optical field control. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 CaYAlO4crystal 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 MoTe2optical 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 MoTe2as 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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 (N 2 RR), CO 2 reduction reaction (CO 2 RR) 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, NO 2 RR and CO 2 RR electrocatalysts. [Display omitted] • Recent development and suggested approaches of various MXenes nanomaterials synthesis, and properties. • MXenes as an electrocatalysts and environmental remediation. • Optimized strategies to improve MXenes compatibility. • Current challenges and future suggestions. [ABSTRACT FROM AUTHOR]

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–Pérot 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. [ABSTRACT FROM PUBLISHER]

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 \mboxpm/\mu\varepsilon at the range of 0–500 $\mu\varepsilon$, while those of the FBG part are 8.40 pm/°C and 1.40 \mbox{pm} /\mu\varepsilon, respectively. The sensitivity difference ensures good simultaneous measurement performance. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

We investigated the fiber Bragg grating (FBG) thermal response in space vacuum thermal environment. The FBGs were packaged with 6061-T6 aluminum. The liquid nitrogen immersion experiment results show that its wavelength shift standard deviation is 0.76 pm for 217 h. The combination effect of vacuum and cryogenic temperature was studied by thermal cycling process in space environment simulator. The FBG sensors show accuracy better than 2% full scale, and the hysteresis errors are below 1%. It proves that these metal packaged FBG sensors can survive and meet the requirement of space measurement. [ABSTRACT FROM AUTHOR]

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. [Display omitted] [ABSTRACT FROM AUTHOR]

Group IVB transition metal dichalcogenides (TMDs) have attracted significant interests in photoelectronics due to their predictable superior physical properties compared to group VIB (Mo and W) TMDs. However, the nonlinear optical properties and ultrafast photonic devices based on group IVB TMDs remained unexplored so far. Herein, the nonlinear optical absorption of HfS2 nanosheets (NSs) prepared by liquid exfoliation is demonstrated. The usage of HfS2 as a new ultrafast photonic device for high‐energy and ultrashort pulse generation in a fiber laser is reported for the first time. A photonic crystal fiber (PCF) assisted deposition method is presented for the fabrication of an HfS2‐microfiber integrated saturable absorber (SA) device with precisely controllable light–matter interaction, which can benefit the output of the device. The HfS2‐microfiber SA device shows modulation depth of 15.7% and exhibits outstanding ultrashort pulse generation performance with pulse duration of 221.7 fs in the communication band. The experimental results suggest that HfS2 presents highly nonlinear optical absorption and can be developed into an excellent candidate of SA devices for the development of HfS2‐based ultrafast photonics. The nonlinear optical absorption of HfS2 nanosheets is demonstrated. Based on this nonlinear optical property, an HfS2‐based ultrafast photonic device is fabricated by integrating HfS2 with a microfiber. The usage of HfS2 for a new function of nonlinear optical materials in the generation of high‐energy and ultrashort pulses by fiber laser is reported. [ABSTRACT FROM AUTHOR]

• The high output power at 1.8 μm could be achieved from a Tm:YAP laser. • The polarizations of the laser beams at 1.82 μm and 1.84 μm are orthogonal. • The 1.82 μm is the shortest wavelength achieved from a CWML Tm-doped bulk laser. 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. [ABSTRACT FROM AUTHOR]

Deuterium-based isotopic labeling is an important technique for tracking cellular metabolism with the Raman signals analysis of low-wavenumber (LW) C-D bonds and high-wavenumber (HW) C-H bonds. We propose and demonstrate a disposable ultra-miniature fiber probe to detect LW and HW coherent anti-Stokes Raman scattering (CARS) spectra for deuterated compounds simultaneously and bond-selectively sensing. The 10.78 µm diameter disposable fiber probe, comprised of focusing taper as fiber probe head and time-domain walk-off eliminating fiber section with designed length, realizes wide-frequency-interval dual Stokes pulse delivering and focusing. The fiber probe enables quantitative concentration determination with resolution down to 11 mM. The chemical vibration modes of LW region C-D bonds and HW region C-H bonds of the mixture samples of organic compounds and their deuterated counterparts in a simulated cell are simultaneously excited and characterized. The CARS disposable fiber probe introduces a promising handle for in vivo biochemical detection based on isotopic labeling sensing.

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-MoS 2 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.

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 2 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.

We demonstrate the HfSe 2 saturable absorber (SA) for the generation of ultrafast pulse laser. The HfSe 2 SA device is fabricated by integrating HfSe 2 nanosheets (NSs) with a microfiber. The material and optical characteristics of HfSe 2 NSs show their high quality. The nonlinear optical absorption of HfSe 2 SA is measured with a modulation depth of 5.8%. Stable soliton mode-locked laser based on HfSe 2 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 HfSe 2 is a good candidate of SA for high efficient ultrashort pulses generation.

A passively mode-locked thulium-doped fiber laser using a tungsten ditelluride saturable absorber (${{\rm WTe}_2}\mbox{-}{\rm SA}$WTe 2 -SA) is demonstrated. High-power mode-locked pulses with an average output power of 108.1 mW were achieved by incorporating the ${{\rm WTe}_2}\mbox{-}{\rm SA}$WTe 2 -SA into a thulium-doped fiber oscillator. To the best of our knowledge, this is the highest average power obtained from a ${{\rm WTe}_2}\mbox{-}{\rm SA}$WTe 2 -SA-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 ${{\rm WTe}_2}\mbox{-}{\rm SA}$WTe 2 -SA could be an excellent candidate for a high-power fiber laser system.

With the magnetron-sputtering deposition method, α phase indium selenide (α-In 2 Se 3 ) was developed into a saturable absorber (SA) with wideband saturable absorption property at 800, 1560, and 1930 nm. After inserting the α-In 2 Se 3 SA into erbium-doped fiber laser (EDFL) and thulium-doped fiber laser (TDFL) systems, we can easily obtain stable soliton pulse trains. The pulse duration/pulse energy/slope efficiency for EDFL and TDFL were 276 fs/2.03 nJ/15.8% and 1.02 ps/7.1 nJ/23.5%, respectively. These results showed that the MSD-grown α-In 2 Se 3 could be regarded as high efficiency material to be applied in ultrafast photonics.

A passively mode-locked thulium-doped fiber (TDF) laser was realized by employing chemical vapor deposited few-layer molybdenum ditelluride (MoTe 2 ) as a saturable absorber (SA). The few-layer MoTe 2 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.

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 2 . Large-area and high quality lattice MoSe 2 grown by chemical vapor deposition method was adopted as an optical modulator for the first time. The large-area MoSe 2 shows excellent nonlinear optical absorption with a large modulation depth of 21.7% and small saturable intensity of 9.4 MW cm -2 . After incorporating the MoSe 2 optical modulator into fiber laser cavity as a saturable absorber, a highly stable Q-switching operation with single pulse energy of 224 nJ is achieved. The large-area MoSe 2 possessing superior nonlinear optical properties compared to exfoliated nanoflakes affords possibility for the larger-area two-dimensional materials family as high performance optical devices.

Ultrafast pulse generation was demonstrated in a thulium-doped fiber laser mode-locked by magnetron-sputtering deposited WTe 2 with a modulation depth, a nonsaturable loss, and a saturable intensity of 31%, 34.3%, and 7.6  MW/cm 2 , respectively. Stable soliton pulses could be obtained at a 1915.5 nm central wavelength with a pulse duration of 1.25 ps, an average output power of 39.9 mW, and a signal-to-noise ratio of 95 dB. To the best of our knowledge, this was the first demonstration of WTe 2 -based saturable absorbers in fiber lasers at a 2 μm regime.

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 2 and its applications in ultrafast photonics have not yet been fully investigated. In this work, the saturable absorption of chemical vapor deposition (CVD) grown WSe 2 films with large-scale and high quality are studied and the use of WSe 2 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 WSe 2 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 WSe 2 film. The integrated microfiber-WSe 2 device shows a large modulation depth of 54.5%. Using the large-area WSe 2 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 WSe 2 films afford an excellent broadband SA for ultrafast photonic applications.

In this Letter, high-quality WS 2 film and MoS 2 film were vertically stacked on the tip of a single-mode fiber in turns to form heterostructure (WS 2 -MoS 2 -WS 2 )-based saturable absorbers with all-fiber integrated features. Their nonlinear saturable absorption properties were remarkable, such as a large modulation depth (∼16.99%) and a small saturable intensity (6.23  MW·cm -2 ). Stable pulses at 1.55 μm with duration as short as 296 fs and average power as high as 25 mW were obtained in an erbium-doped fiber laser system. The results demonstrate that the proposed heterostructures own remarkable nonlinear optical properties and offer a platform for adjusting nonlinear optical properties by stacking different transition-metal dichalcogenides or modifying the thickness of each layer, paving the way for engineering functional ultrafast photonics devices with desirable properties.

In this paper, we demonstrate a high-damage-resistant tungsten disulfide saturable absorber mirror (WS 2 -SAM) fabricated by magnetron sputtering technique. The WS 2 -SAM has an all-fiber-integrated configuration and high-damage-resistant merit because the WS 2 layer is protected by gold film so as to avoid being oxidized and destroyed at high pump power. Employing the WS 2 -SAM in an Erbium-doped fiber laser (EDFL) with linear cavity, the stable Q-switching operation is achieved at central wavelength of 1560 nm, with the repetition rates ranging from 29.5 kHz to 367.8 kHz and the pulse duration ranging from 1.269 μs to 154.9 ns. For the condition of the maximum pump power of 600 mW, the WS 2 -SAM still works stably with an output power of 25.2 mW, pulse energy of 68.5 nJ, and signal-noise-ratio of 42 dB. The proposed WS 2 -SAM configuration provides a promising solution for advanced pulsed fiber lasers with the characteristics of high damage resistance, high output energy, and wide tunable frequency.

We propose a novel fiber-optic Fabry-Perot interferometric (FFPI) temperature sensor based on differential pressure resulting from thermal expansion of sealed air. A thin silicon diaphragm is sandwiched between two micro-circular cavity-structured Pyrex plates to construct a FP and an air cavity. The thermal expansion of sealed air induces differential pressure variation between cavities and thus the deformation of thin diaphragm, which transfers temperature change into cavity length shift of FP interferometer. Theory analysis results indicate that the temperature-sensitivity can be designed flexibly by choosing the parameters of radius and thickness of silicon diaphragm, and the differential pressure between two cavities. Experimental results demonstrate that the temperature sensitivity of 6.07 nm/°C is achieved with the resolution of 0.10°C under the range of -50°C to 100°C, and the response time is around 1.3 s with temperature change from 28°C to 100°C.

We present a high precision and fast speed demodulation method for a polarized low-coherence interferometer with location-dependent birefringence dispersion. Based on the characteristics of location-dependent birefringence dispersion and five-step phase-shifting technology, the method accurately retrieves the peak position of zero-fringe at the central wavelength, which avoids the fringe order ambiguity. The method processes data only in the spatial domain and reduces the computational load greatly. We successfully demonstrated the effectiveness of the proposed method in an optical fiber Fabry-Perot barometric pressure sensing experiment system. Measurement precision of 0.091 kPa was realized in the pressure range of 160 kPa, and computation time was improved by 10 times compared to the traditional phase-based method that requires Fourier transform operation.

We propose a new wavelength-division-multiplexing method for extrinsic fiber Fabry-Perot interferometric (EFPI) sensing in a polarized low-coherence interferometer configuration. In the proposed method, multiple LED sources are used with different center wavelengths, and each LED is used by a specific sensing channel, and therefore the spatial frequency of the low-coherence interferogram of each channel can be separated. A bandpass filter is used to extract the low-coherence interferogram of each EFPI channel, and thus the cavity length of each EFPI channel can be identified through demultiplexing. We successfully demonstrate the simultaneous demodulation of EFPI sensors with same nominal cavity length while maintaining high measurement precision.

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 π ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method.

A demodulation algorithm based on absolute phase recovery of a selected monochromatic frequency is proposed for optical fiber Fabry-Perot pressure sensing system. The algorithm uses Fourier transform to get the relative phase and intercept of the unwrapped phase-frequency linear fit curve to identify its interference-order, which are then used to recover the absolute phase. A simplified mathematical model of the polarized low-coherence interference fringes was established to illustrate the principle of the proposed algorithm. Phase unwrapping and the selection of monochromatic frequency were discussed in detail. Pressure measurement experiment was carried out to verify the effectiveness of the proposed algorithm. Results showed that the demodulation precision by our algorithm could reach up to 0.15kPa, which has been improved by 13 times comparing with phase slope based algorithm.