In this paper, a novel optical fiber surface plasmon resonance (SPR) magnetic field sensor is proposed and experimentally demonstrated. The structure is fabricated by splicing a section of photonic crystal fiber between two multimode fibers. After the structure is coated with 10 nm Cr and 50 nm Au, the high refractive index (RI) sensitivity, from 1973.72 nm RIU−1 to 3223.32 nm RIU−1 in the range of 1.3326–1.3680, verifies the SPR sensor, which is higher than the structure based on single mode fiber with the same coating. In addition, the microscopic mechanism of the tunable characteristics of magnetic fluid RI with the ambient magnetic field is simulated by the molecular dynamics method. To measure the external magnetic field, the sensing region of the SPR sensor is fully inserted in a capillary tube, which is filled with magnetic fluid and sealed with UV glue. A maximum sensitivity of 4.42 nm mT−1 is achieved in the range of 0–24 mT, experimentally. Due to high sensitivity, simple manufacturing and compact size, the proposed sensor possesses attractive application prospects in environmental monitoring, power transmission and biomedical applications.

Optical fiber SPR magnetic field sensor based on photonic crystal fiber with the magnetic fluid as cladding

A novel compact ultra-high sensitivity optical fiber temperature sensor based on surface plasmon resonance (SPR) is proposed and demonstrated. The sensor is fabricated by employing a helical-core fiber (HCF), which is polished as a D-type fiber on the helical-core region and coated with a layer of Au-film and polydimethylsiloxane (PDMS). The theoretical and experimental results show that the resonant wavelength and sensitivity of the proposed sensor can be effectively adjusted by changing the twisting pitch of HCF. Due to the high refractive index sensitivity of the sensor and the high thermo-optic coefficient of PDMS, the maximum sensitivity can reach -19.56 nm/°C at room temperature when the twist pitch of HCF is 2.1 mm. It is worth noting that the sensitivity can be further improved by using a shorter pitch of HCF. The proposed SPR temperature sensor has adjustable sensitivity, is easy to realize distributed sensing, and has potential application prospects in biomedical, healthcare, and other fields.

Ultra-high sensitivity SPR temperature sensor based on a helical-core fiber.

In the present work, we introduced a highly sensitive vibration sensor, which is based on the dispersion turning point (DTP) microfiber Mach-Zehnder interferometer. The axial strain and vibration sensing characteristics of the microfiber Mach-Zehnder interferometer were investigated. First, we theoretically analyzed the spectrum evolution characteristics of the microfiber Mach-Zehnder interferometer caused by axial strain. Second, the microfiber with different diameters was fabricated using the electrode discharge and fused taper method, and the axial strain experiments were conducted; the maximum sensitivity of the DTP microfiber with a diameter of ∼2.2 µm reached -45.55 pm/µɛ at ∼1550 nm. Finally, based on the axial strain principle of the microfiber, we designed a highly sensitive vibration sensor using a DTP microfiber integrated into a rectangular through-hole cantilever beam. The 30-3500 Hz vibration signal monitoring could be realized, the maximum signal-to-noise ratio (SNR) was ∼75 dB at 52 Hz, and the acceleration sensitivity reached as high as 0.764 V/g at 45Hz. These results suggested the high performance of the microfiber in axial strain and micro-vibration sensing fields.

Highly sensitive vibration sensor based on the dispersion turning point microfiber Mach-Zehnder interferometer

A fiber-optic sensor for chemically aggressive environments, such as concentrated solutions of acids and alkalis, has been manufactured The sensor is based on a single-mode optical fiber with a chemically etched cladding, coated with a thin film of tin dioxide (SnO2) by metalorganic chemical vapor deposition (MOCVD) In the transmission spectra of a SnO2 coated taper lossy mode resonances (LMRs) were observed, the maximum of which shifted to the long-wavelength part of the spectrum, with an increase in the thickness of the deposited film At a deposition temperature of 345 °C, it was possible to detect the separation of the transverse electric (TE) and transverse magnetic (TM) LMRs for resonances up to the third order From the change in the position of the 1-st TE LMR, the refractive index and the molar concentration of acids and alkalis in such aggressive liquids as aqueous solutions of HCl, HNO3, H2SO4, NaOH were determined, which, according to our information, is demonstrated for the first time The high chemical durability of the coating was confirmed by its insusceptibility to aqua regia (AR) The sensitivity of the sensor to changes in the surrounding medium refractive index (SMRI) and the molar concentration of acids was more than 5260 nm/RIU and 32 nm/M, respectively

Fiber optic Lossy Mode Resonance based sensor for aggressive liquids

In this paper, we propose a highly sensitive temperature sensor based on two cascaded Mach–Zehnder interferometers (MZIs) that work using the Vernier effect. The all-fiber MZIs were assembled by splicing a segment of capillary hollow-core fiber (CHCF) between two sections of multimode fibers (MMFs). This cascaded configuration exhibits a temperature sensitivity of 1.964 nm/°C in a range from 10 to 70 °C, which is ~67.03 times higher than the sensitivity of the single MZI. Moreover, this device exhibits a high-temperature resolution of 0.0153 °C. A numerical analysis was carried out to estimate the devices’ temperature sensitivity and calculate the magnification of the sensitivity produced by the Vernier effect. The numerical results have an excellent agreement with the experimental results and provide a better insight into the working principle of the MZI devices. The sensor’s performance, small size, and easy fabrication make us believe that it is an attractive candidate for temperature measurement in biological applications.

In-Line Mach-Zehnder Interferometers Based on a Capillary Hollow-Core Fiber Using Vernier Effect for a Highly Sensitive Temperature Sensor.

In the traditional Mach–Zehnder interferometer, only one phase matching condition needs to be satisfied for destructive interference. Here, we propose and demonstrate a Mach–Zehnder interferometer with double phase matching condition, which satisfies both the destructive condition of double beam interference and the resonant condition of anti-resonant effect. Different from the traditional method, the interference is construed as a coherent superposition between anti-resonant beam and cladding one. The effect of the multimode fiber length on the energy distribution and transmission spectrum is analyzed precisely. The experimental results show that the intensity of the wavelength meeting double phase matching condition is extremely sensitive to both strain and temperature. The maximum intensity sensitivity to strain and temperature are up to 16.1 dB/mv and 0.181 dB/°C, respectively. Compared with the previous work, the sensitivities have been improved several times or even tens of times. The proposed Mach–Zehnder interferometer with double phase matching condition can improve the dip depth, which has a great potential value in sensing application.

Double Phase Matching in MZI With Antiresonant Effect for Optical Fiber Sensor Application

A surface plasmon resonance (SPR) temperature sensor on the basis of depressed double cladding fiber (DDCF) is theoretically proposed and experimentally demonstrated for the first time. Simulation analysis implies that the SPR fiber optic structure consisting of a multimode fiber (MMF) inserted into an 8 mm long DDCF is highly sensitive to the refractive index (RI) of the surrounding environment, owing to their mismatched cores, large discrepancy in cladding diameters, and the depressed inner cladding in DDCF. The experimental results further verify that the highest RI sensitivity is 7002 nm/RIU established with a 50nm Au coated DDCF-SPR sensor. Additionally, the temperature sensitivity reaches up to −2.27 nm/°C within a wide working temperature range of −30 to 330 °C by combining polydimethylsiloxane (PDMS) film as the temperature sensitive material with DDCF-Au architecture. The integrated PDMS, Au and DDCF temperature sensor possesses high performance in terms of sensing capability and physical construction, opening a route to their potential applications in other types of sensors.

Ultrawide temperature range operation of SPR sensor utilizing a depressed double cladding fiber coated with Au-Polydimethylsiloxane

We design and investigate a hybrid plasmonic nanofocusing waveguide (HPNW) for surface-enhanced Raman scattering (SERS) tweezer applied to the on-chip Raman detection and optical trapping. The input mode from the dielectric waveguide can be well coupled into the surface plasmon polariton (SPP) mode of plasmonic waveguide. During this procedure, the HPNW can compress the mode field, thereby significantly enhancing the spot electric field inside the gold slot, where the SERS can be excited coincided with the optical trapping of sample particles. Meanwhile, the Raman scattered light can be collected by the HPNW itself, without other external devices. The electric field enhancement factor, optical trapping potential and the collection efficiency of scattered light are utilized to study and characterize the performance of the SERS tweezer. The simulation results indicate that the optimized SERS tweezer can trap a 20 nm diameter sample particle with only 20 mW excitation power. As far as we know, this is the first time that the SERS tweezer combining both the SERS detection and optical trapping is proposed in an on-chip photonic waveguide.

Hybrid plasmonic nanofocusing waveguide for on-chip SERS tweezer

Optical computing and optical neural network have gained increasing attention in recent years because of their potential advantages of parallel processing at the speed of light and low power consumption by comparison with electronic computing. The optical implementation of the fundamental building blocks of a digital computer, i.e. logic gates, has been investigated extensively in the past few decades. Optical logic gate computing is an alternative approach to various analogue optical computing architectures. In this paper, the latest development of optical logic gate computing with different kinds of implementations is reviewed. Firstly, the basic concepts of analogue and digital computing with logic gates in the electronic and optical domains are introduced. And then a comprehensive summary of various optical logic gate schemes including spatial encoding of light field, semiconductor optical amplifiers (SOA), highly nonlinear fiber (HNLF), microscale and nanoscale waveguides, and photonic crystal structures is presented. To conclude, the formidable challenges in developing practical all-optical logic gates are analyzed and the prospects of the future are discussed. al. All-optical logic gate computing for high-speed parallel information processing. Opto-Electron Sci 1 , 220010 (2022).

https://www.oejournal.org/data/article/export-pdf?id=63184bb899d88169526cc188

All-optical logic gate computing for high-speed parallel information processing

It is still a challenge to realize the absolute optical path difference (OPD) demodulation of multi-interference systems with a narrow spectral interval and small OPD interval In this paper, an iterative normalized cross-correlation algorithm is firstly proposed for demodulating the multiple absolute OPDs of a dual-interference system and applied to optical fiber sensing system By constructing a template function in combined form, the optimal solutions of its components and OPDs are solved iteratively based on the reconstruction matrix method and cross-correlation algorithm, respectively The simulation and experiment show that the demodulation accuracies near the OPDs of 560 µm and 660 µm are both up to 5 nm in different spectral intervals from 45 to 80 nm The simulation results show that all demodulation precisions at the spectral interval of 55 nm do not exceed 4 nm when the OPD changes in the range of 650-670 µm Besides, the experimental verification shows the temperature accuracy (0125 °C) with 95% confidence of T-distribution is very close to the control accuracy (01 °C) The proposed algorithm can improve the multiplexing capability of optical fiber sensor system and reduce its cost

Guomeng Zuo

Papers

Double Phase Matching in MZI With Antiresonant Effect for Optical Fiber Sensor Application

Ultrawide temperature range operation of SPR sensor utilizing a depressed double cladding fiber coated with Au-Polydimethylsiloxane

Hybrid plasmonic nanofocusing waveguide for on-chip SERS tweezer

All-optical logic gate computing for high-speed parallel information processing

Iterative normalized cross-correlation method for absolute optical path difference demodulation of dual interferometers.