Ultra-sensitive all-optical phase modulation based on a fiber optic interferometer combined with TiCT MXene-incorporated PDMS.

This study proposes an all-optical phase modulator based on a compact fiber optic interferometer combined with TiCT MXene-incorporated PDMS. Due to the high photothermal conversion efficiency of MXene and the high thermo-optic coefficient of PDMS, changes in pump power can be effectively converted into refractive index (RI) variations in the PDMS. Then, by employing a fiber optic interferometer with a high RI response, ultra-sensitive all-optical phase modulation can be realized.

Titanium Nitride Modified Fiber Optic Interferometer for Refractive Index Sensitivity Enhancement.

As one of the most well-established biocompatible transition metal nitrides, titanium nitride (TiN) has been widely applied for fiber waveguide coupling device applications. This study proposes a TiN-modified fiber optic interferometer. Benefiting from the unique properties of TiN, including ultrathin nanolayer, high refractive index, and broad-spectrum optical absorption, the refractive index (RI) response of the interferometer is greatly enhanced, which is desired all the time in the field of biosensing.

Femtosecond laser written ultra-weak Fabry-Perot array for distributed absolute temperature profile sensing with high spatial resolution.

In this paper, high spatial-resolution distributed temperature sensing has been realized based on a femtosecond laser written ultra-weak Fabry-Perot Array (FPA). 50 identical Fabry-Perot cavities are fabricated in a 10 mm long optical fiber by femtosecond laser point-by-point written technology, and the corresponding spatial resolution is as high as 200 µm. Besides, by employing the total phase demodulation method, the optical path lengths (OPLs) in the ultra-weak FPA are successively demodulated based on the Rayleigh backscattering signal recorded by an optical frequency domain reflectometry (OFDR), and therefore the absolute temperature values instead of the relative ones can be obtained.

Ultrasensitive deafness gene DNA hybridization detection employing a fiber optic Mach-Zehnder interferometer: Enabled by a black phosphorus nanointerface.

The rapid and efficient detection of deafness gene DNA plays an important role in the clinical diagnosis of deafness diseases. This study demonstrates the ultrasensitive detection of complementary DNA (cDNA) by employing a nanointerface-sensitized fiber optic biosensor. The sensor consists of SMF-TNCF-MMF-SMF (abbreviated as STMS) structure with lateral offset.

TiCN MXene-based ultra-sensitive optical fiber salinity sensor.

A TiCN MXene enabled ultra-sensitive optical fiber sensor is proposed, and a salinity measurement is conducted to evaluate its sensing performance in a low-concentration target molecule detection environment. Owing to the abundance of hydrophilic functional groups (-O, -F, and -OH), large specific surface, and broad-spectrum absorption characteristics of the MXene layers, the sensing performance of the MXene-incorporated sensor is greatly improved and an ultra-high salinity sensitivity of -5.34 nm/‰ is achieved (equivalent to a refractive index sensitivity of -33429 nm/RIU).

Multiplexed Weak Waist-Enlarged Fiber Taper Curvature Sensor and Its Rapid Inline Fabrication.

This study proposes a multiplexed weak waist-enlarged fiber taper (WWFT) curvature sensor and its rapid fabrication method. Compared with other types of fiber taper, the proposed WWFT has no difference in appearance with the single mode fiber and has ultralow insertion loss. The fabrication of WWFT also does not need the repeated cleaving and splicing process, and thereby could be rapidly embedded into the inline sensing fiber without splicing point, which greatly enhances the sensor solidity.

High-sensitivity and large-range fiber optic temperature sensor based on PDMS-coated Mach-Zehnder interferometer combined with FBG.

Although numerous efforts have been dedicated towards developing fiber sensors with high performances, challenges still remain in achieving high-quality temperature sensors with high sensitivity, large measurement range and high stability. This study proposes a compact fiber optic temperature sensor based on PDMS-coated Mach-Zehnder interferometer (MZI) combined with FBG, and it can realize both high-sensitivity and large-range temperature measurement. The MZI is based on Thin No-Core Fiber (TNCF) with lateral-offset.

Four-wave mixing-based photonic crystal fiber microfluid sensor with embedded U-shape microslits.

In this paper, we propose a four-wave mixing-based photonic crystal fiber (PCF) microfluid sensor, and two U-shape microslits fabricated by a femtosecond laser are embedded into the sensor for real-time microfluid measurement. Theoretical and experimental results prove that the signal wavelength is sensitive to both the refractive index (RI) and the material dispersion property of the liquid sample filled into the air channels. For different aqueous target samples at low concentrations, the responses of signal wavelength are consistent with each other.

Interrogation technique analyses of a hybrid fiber optic sensor based on SPR and MMI.

This study evaluates the interrogation techniques of a hybrid fiber optic sensor based on surface plasmon resonance (SPR) and multimode interference (MMI). The sensor is based on a single mode, fiber-no core, fiber-single mode fiber (SMF-NCF-SMF) structure with a deposited gold film layer. Both SPR and MMI effects are excited in a single sensor structure without enlarging the device size.

High-performance fiber sensor via Mach-Zehnder interferometer based on immersing exposed-core microstructure fiber in oriented liquid crystals.

Rapid technology development and various applications show great demands for high-quality temperature sensors with super-sensitivity, broad working temperature ranges, excellent linearity and high stability. Although tremendous efforts have been dedicated towards developing fiber sensors with high performance, challenges still remain in achieving all of the four parameters. Herein, we fabricate a fiber sensor via a Mach-Zehnder interferometer (MZI) combined with a liquid crystal (LC)-filled microtube, where the LC in the microtube is uniformly orientated.

Zinc oxide-black phosphorus composites for ultrasensitive nitrogen dioxide sensing.

Multi-layer black phosphorus (m-BP) has been successfully incorporated in zinc oxide (ZnO) hollow spheres, thus forming hetero-structured ZnO-BP composites; a study performed on their properties reveals that the BP environmental stability can be significantly enhanced by the introduction of ZnO, and the sensors based on ZnO-BP composites exhibit high response, fast response behavior, outstanding selectivity, and ultralow detection limit of 1 ppb towards NO gas molecules. The ultrasensitive sensing performance is suggested to be due to the large surface area, excellent carrier mobility, and enhanced charge transfer of ZnO-BP in the presence of BP. Moreover, the mechanism of NO sensing with ZnO-BP is confirmed by the calculations obtained from the first-principle studies.

A Simplified Hollow-Core Photonic Crystal Fiber SERS Probe with a Fully Filled Photoreduction Silver Nanoprism.

In this paper, a simplified hollow-core photonic crystal fiber surface-enhanced Raman scattering (SERS) probe is presented. Silver nanoprisms are grown with a photoreduction method and account for the SERS, which have better electromagnetic enhancement than spherical silver nanoparticles at 785 nm. Due to the antiresonant reflecting guidance mechanism, the excited laser and SERS signal are effectively guided in such a fully filled hollow-core photonic crystal fiber SERS probe and complicated selective filling with target sample is avoided.

UV-Enhanced Ethanol Sensing Properties of RF Magnetron-Sputtered ZnO Film.

ZnO film was deposited by the magnetron sputtering method. The thickness of ZnO film is approximately 2 μm. The influence of UV light illumination on C₂H₅OH sensing properties of ZnO film was investigated.

Photoreduced silver nanoparticles grown on femtosecond laser ablated, D-shaped fiber probe for surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS) probes are made by facile photochemical deposition of silver nanoparticles on a femtosecond (fs) laser ablated, D-shaped fiber. The structure and surface morphology of the probe are investigated by scanning electron microscopy. High-quality SERS signals are detected using Rhodamine 6G molecules via an in situ sensing mode.

All-fiber reflecting temperature probe based on the simplified hollow-core photonic crystal fiber filled with aqueous quantum dot solution.

An all-fiber reflecting fluorescent temperature probe is proposed based on the simplified hollow-core photonic crystal fiber (SHC-PCF) filled with an aqueous CdSe/ZnS quantum dot solution. SHC-PCF is an excellent PCF used to fill liquid materials, which has low loss transmission bands in the visible wavelength range and enlarged core sizes. Both end faces of the SHC-PCF were spliced with multimode fiber after filling in order to generate a more stable and robust waveguide structure.

V-groove all-fiber core-cladding intermodal interferometer for high-temperature sensing.

Novel V-groove all-fiber core-cladding intermodal interferometers fabricated by CO2 laser irradiation on a standard single-mode fiber are described. The high-order cladding modes are excited due to the special V-groove structure. The interferometers are classified as Mach-Zehnder and Michelson type based on the way they are structured.

High temperature microstructured fiber sensor based on a partial-reflection-enabled intrinsic Fabry-Perot interferometer.

A compact fiber Fabry-Perot interferometer (FPI) sensor for high temperature measurements is proposed and demonstrated. The FPI consists of a small core microstructured fiber and single mode fiber, and it is enabled by partial Fresnel reflection at the interface of the two fibers and the end surface Fresnel reflection of the microstructured fiber. Simple splicing and cleaving techniques are used to construct such an interferometer, and the fringe contrast can reach 20 dB.

In-line flat-top comb filter based on a cascaded all-solid photonic bandgap fiber intermodal interferometer.

In this paper, an in-line comb filter with flat-top spectral response is proposed and constructed based on a cascaded all-solid photonic bandgap fiber modal interferometer. It consists of two short pieces of all-solid photonic bandgap fiber and two standard single-mode fibers as lead fibers with core-offset splices between them. The theoretical and experimental results demonstrated that by employing a cut and resplice process on the central position of all-solid photonic bandgap fiber, the interference spectra are well tailored and flat-top spectral profiles could be realized by the controllable offset amount of the resplice.

Mode-beating-enabled stopband narrowing in all-solid photonic bandgap fiber and sensing applications.

In this paper, core-cladding modal beating in a short piece of all-solid photonic bandgap fiber (AS-PBF) is observed in longitudinal propagation direction. It is demonstrated that at the stopband range of AS-PBF, the power could transfer back and forth between the fiber core and the first layer of high-index rods. Both experimental results and the theoretical analysis from transverse coupled mode theory confirm that the 3-dB width of the sharp stopband could be significantly narrowed by multicycles of such core-cladding modal couplings, which is of great benefit to the high-resolution sensing applications.

Sensitivity-enhanced high-temperature sensing using all-solid photonic bandgap fiber modal interference.

A wavelength-encoded interferometric high-temperature sensor based on an all-solid photonic bandgap fiber (AS-PBF) is reported. It consists of a small piece of AS-PBF spliced core offset with standard single-mode fibers. Two core modes LP(01) and LP(11) are conveniently utilized as optical arms to form Mach-Zehnder-type interference at both the first and the second photonic bandgaps, and the maximum extinction ratio exceeds 25 dB.

Some features of the photonic crystal fiber temperature sensor with liquid ethanol filling.

We introduce a novel photonic crystal fiber (PCF) temperature sensor that is based on intensity modulation and liquid ethanol filling of air holes with index-guiding PCF. The mode field, the effective refractive index and the confinement loss of PCF were all found to become highly temperature-dependent when the thermo-optic coefficient of the liquid ethanol used is higher than that of silicon dioxide and this temperature dependence is an increasing function of the d/Lambda ratio and the input wavelength. All the experiments and simulations are discussed in this paper and the temperature sensitivity of transmission power was experimentally determined to be 0.