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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]

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]

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.

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.

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.