D-shaped Fiber Research Articles

Dual-Wavelength Q-switched Fiber Laser Generation by Incorporating 2D Materials in D-SMS Fiber Structure

We demonstrate a dual-wavelength Q-switched fiber laser generation by inserting a combination of SM-MM-SM fiber and a d-shape structure. This combination is known as D-SMS fiber. By side-polishing an SM fiber with 1-dB loss, the d-shape fiber structure is obtained. Then the d-shape SM fiber is spliced to 25 cm long MM and SM fiber to form a D-SMS fiber structure. After inserting D-SMS fiber, a stable dual-wavelength presence at 1562.8 nm and 1563.8 nm (1 nm wavelength spacing). The pulse train generates once we deposited a graphene oxide solution onto the surface of the d-shape structure. This Q-switching operation mode obtained from 45 mW to 111 mW pump power with a maximum pulse energy of 56 nJ. The repetition rate and pulse width have been recorded from 34 kHz to 55 kHz and from 10.22 µs to 6.47 µs, respectively.

Highly sensitive MoS2/graphene based D-shaped optical fiber SPR refractive index sensor with Ag/Au grated structure

Highly sensitive MoS2/graphene based D-shaped optical fiber SPR refractive index sensor with Ag/Au grated structure

Characterization of incompletely coated D-shaped PCF-SPR refractive index sensors

To reduce the complexity of the sensor structure and improve the sensitivity of refractive index (RI) measurement, a D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) RI sensor with incomplete coating of gold-tantalum pentoxide (Au-Ta2O5) on the surface is proposed. When the coating width is 3.1 μm, the sensor can detect RI samples ranging from 1.35 to 1.41 in the ultra-wide near-infrared (NIR) region of 1100–2100 nm wavelength. Its maximum wavelength sensitivity is 20,000 nm RIU−1, maximum amplitude sensitivity is 2817.7 RIU−1, resolution is RIU, and figure of merit (FOM) is 333.3 RIU−1. This sensor can be widely used in biological tissue detection. For this type of incomplete coated D-shaped sensor, the coating material and structural parameters not only affect the performance of the sensor, but also change the RI detection range, which has been ignored or not mentioned in previous literature on PCF-SPR sensors. Therefore, the reasons for the change of RI detection interval and negative optimization caused by structural parameters were analyzed, and two different sensors with different coating widths were finally obtained, which can achieve high sensitivity sensing in their respective detection intervals. The detailed research results expand the understanding of the SPR phenomenon in D-shaped PCF and provide theoretical guidance for adjusting and improving the detection performance of PCF-SPR sensors.

Numerical study of a D-shaped optical fiber SPR biosensor for monitoring refractive index variations in biological tissue via a thin layer of gold coated with titanium dioxide

This study aims to explore the numerical analysis of the impact of integrating titanium oxide (TiO2) into a D-shaped optical fiber biosensor based on surface plasmon resonance (SPR). A thin layer of gold (Au) is applied to the flat section of the fiber, which is also coated with a thin layer of titanium dioxide (TiO2). The behavior and performance of the proposed biosensor for use in biological environments are evaluated using the finite element method (FEM). The optical response of SPR-based biosensors is highly dependent on the analyzed medium, enabling the detection of pathogenic cells and abnormalities in biological tissues. This provides high sensitivity and selectivity, as well as real-time detection accuracy and speed. In this study, the biosensor is incorporated into a biological medium with a refractive index that varies with wavelength. A series of simulations have been conducted to plot the spectra of transmissions, absorptions, and dielectric losses obtained in the output of the sensor instrument. From these spectra, the corresponding surface plasmon resonance (SPR) wavelength (λSPR) within the visible-near-infrared band can be determined. Taking into account the various parameters that influence plasmonic interactions, the biosensor's performance parameters, in particular sensitivity and refractive index resolution have been optimized. Our results show that the presence of the TiO2 layer improves the performance of the proposed sensor and offers the possibility of adjusting the resonance wavelength (λSPR). In addition, our proposed sensor can achieve a better resolution of 7.50×10-6[RIU] in 1.34-143 range of analyte refractive index, which notably exceeds that of current technologies. This opens up new prospects in the field of chemical and biological detection.

D-shaped microstructure fiber temperature sensor based on surface plasmon resonance

In order to solve the problems of oxidation of the metal film coated on the outer surface of the photonic crystal fiber and the low sensitivity of the sensor, a side polishing temperature sensor based on surface plasmon resonance is proposed. First, the sensor is modelled with a metal coating on the side of the optical fiber of the sensor, using a temperature sensitive liquid as the temperature sensing substance. Then, simulations were carried out to calculate the structural parameters of the optical fiber and the effect of the metal material on the resonant wavelength of the loss spectrum. By comparing the sensitive sensing of different metal films, gold was chosen as the surface plasma sensing material. Finally, the sensing characteristics of the sensor are simulated using the finite element method. The results show that when gold is used as the surface plasmon material, the wavelength range is 675–1117 nm, and the high sensitivity sensing in the temperature range of 0 °C–60 °C can be realized. When the temperature is 0 °C, the maximum spectral sensitivity is 24.6 nm °C−1. The designed sensors have excellent performance and can be widely used for temperature sensing.

High sensitivity D-shaped fiber decorated with self-assembly Ag nanoparticles for Raman enhancement via collecting backward and vertical direction scattering signals

High sensitivity D-shaped fiber decorated with self-assembly Ag nanoparticles for Raman enhancement via collecting backward and vertical direction scattering signals

Enhanced sensitivity and wide refractive index detection range of D-shaped SPR fiber sensor based on Au/ZnO nanostructures

Enhanced sensitivity and wide refractive index detection range of D-shaped SPR fiber sensor based on Au/ZnO nanostructures

A high-sensitivity D-shaped photonic crystal fiber surface plasmon resonance sensor for low refractive index detection

A high-sensitivity D-shaped photonic crystal fiber surface plasmon resonance sensor for low refractive index detection

Design and Theoretical Analysis of High-Sensitive Surface Plasmon Resonance Sensor Based on Au/Ti 3C2Tx-MXene Hybrid Layered D-Shaped Photonic Crystal Fiber

To achieve high-sensitive refractive index (RI) sensing, an Au/Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> -MXene hybrid layered D-shaped photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) sensor is proposed theoretically. The cladding of the D-shaped PCF has a hexagonal air-hole arrangement. In addition, the two air holes nearest to the metal layer in the first layer of cladding are reduced to enhance the plasma wave and provide an efficient leakage channel. The two air holes second nearest to the metal layer in the same layer are enlarged to limit the light scattering and guide more energy coupled with the surface plasmon polariton (SPP) mode. A thin layer of the Ti3C2Tx-MXene and Au film is applied on the surface of the D-shaped PCF to produce plasmon resonances across a wide range of wavelengths. By using the finite element method, the optical properties of the proposed PCF-SPR sensor are investigated. The results of the numerical analysis show that this sensor has a significant SPR effect, and the resonance loss peaks can be formed at different positions in the wavelength range of 800-2020 nm. The average RI sensitivity reaches 48120 nm/RIU and the maximum sensitivity is up to 64600 nm/RIU in the refractive index range of 1.390-1.415. The RI sensitivity of the Au/Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> -MXene layered sensor is 2.36 times higher than the sensor with only the Au layer. The proposed structure has its unique sensing properties, which can be effectively applied in bio-sensing fields.

Ultra-high sensitivity methane gas sensor based on vernier effect in double D-shaped and cryptophane-A film-coated photonic crystal fiber: Design and FEM simulation

Utilization of the vernier effect in fiber optic interferometers represents the latest approach to enhance the sensitivity and resolution in fiber optic sensors. In this paper, the Vernier effect in Sagnac interference (SI) with a double D-shaped photonic crystal fiber (PCF) was proposed for the methane gas sensing. The sensing arm in the SI was composed of a double D-shaped PCF which was coated with cryptophane-A film, while the polarization maintaining photonic crystal fiber (PM-PCF) is used as the reference arm. The sensing arm and the reference arm were cascaded in parallel to generate the Vernier effect. The influence of the structural parameters in the PCF on the sensing performance was analyzed using the finite element method. The sensing fiber uses a double-D structure, so methane gas is more easily in contact with the sensitive film. According to the simulation results, the wavelength sensitivity of the parallel Sagnac loops within the methane gas concentration range of 0–3.5% is as high as 170.58 nm/%, which is 3.14 times that of a single Sagnac loop. The proposed sensor exhibits a significant enhancement in sensitivity compared to the other fiber optic-based methane gas sensors, thereby providing a reference sample for the development of high-sensitivity methane gas sensors.

Stannic oxide saturable absorbers for generating Q-switched erbium-doped fiber lasers

As a kind of transition metal oxides (TMO), stannic oxide (SnO2) has aroused extensive attention due to its direct bandgap N-type semiconductor property. However, few studies have been focused on the nonlinear property and optical modulation. Herein, passively Q-switched erbium-doped fiber lasers based on SnO2 saturable absorber (SA) are constructed and experimentally verified. To our best knowledge, this is the first report on the optical nonlinearity of SnO2 as a Q-switcher for the near-infrared fiber laser. There are two kinds of SAs fabricated by the filmy and D-shaped fiber (DF) deposition methods. A stable Q-switching operation at 1568 nm was achieved induced by the SnO2 film. After replacing SnO2 film with the SnO2-DF SA, Q-switched operations with an operating wavelength of 1532 nm was achieved. To be noted for a comparison, the performance of 1530 nm Q-switched pulses is obviously improved. Our experimental results could further promote the progress of nonlinear optic and pulsed fiber lasers.

Microfluidic integrated D-shaped optical fiber SERS probe with high sensitivity and ability of multi-molecule detection.

In order to enhance the sensitivity, integration, and practical application capability of Raman detection systems, we propose a multi-channel microfluidic integrated D-shaped optical fiber SERS (Surface-enhanced Raman scattering) probe structure. Firstly, a microfluidic polydimethylsiloxane (PDMS) channel was fabricated using a self-designed multi-channel microfluidic template. Secondly, a uniform layer of silver nanoparticles was deposited on the D-shaped optical fiber using the liquid-liquid interface method. Finally, the D-shaped optical fiber was plasma-bonded to the multi-channel microfluidic channel and a cover glass, resulting in a microfluidic integrated D-shaped optical fiber SERS probe. The prepared sample exhibited excellent detection performance for R6G (rhodamine 6 G) with a detection limit as low as 10-11 mol/L and an enhancement factor of 1.14 × 109. Moreover, the multi-channel configuration enables simultaneous detection of multiple molecules, demonstrating excellent multi-channel multiplexing capability.

A comparative analysis of a D-shaped photonic crystal sensor based on graphene plasmonic

In this paper, a D-shaped photonic crystal fiber (PCF) sensor based on surface plasmon resonance has been presented. In the proposed structure, Graphene, Gold, and Silver have been used in different configurations in order to promote the sensitivity of the sensor. According to the numerical simulations performed by the finite element method (FEM) and considering the refractive index of the analyte from 1.36 to 1.40, the maximum wavelength sensitivity of 12600 nm RIU−1 has been obtained, which is related to the structure when the Gold layer sandwiched between two Graphene layers. This is while, the maximum amplitude sensitivity of the proposed sensor is 5708 (RIU−1), which is related to the configuration that Graphene has been placed under the Silver layer. On the other hand, the proposed structure is easy to use because there is no need to fill the fiber holes with the analyte and it can be easily placed on the D-shaped surface of the sensor. The proposed sensor is appropriate to sense the biological variation because of showing strong surface plasmon resonances. The effect of the fabrication tolerance on the proposed PCF is also studied. It is expected that the proposed model will be compatible with the bio-engineering approaches.

Symmetrical dual D-shape fiber for waveguide coupled surface plasmon resonance sensing

A waveguide-coupled surface plasmon resonance (WCSPR) sensor consisting of two D-shape single-mode fibers is designed and analyzed by the finite element method (FEM). The optical field of the surface plasmon polaritons (SPPs) mode is confined in the dielectric cavity between the dual metallic thin films. Therefore, the effective refractive index of the SPP mode depends largely on the refractive index of the analyte and an anomalous dispersion relationship is observed between the SPP mode and x-polarized core-guide mode of the dual D-shape fiber. The excitation mechanism of surface plasmon resonance (SPR) in the coupling region is attributed to phase matching of the two modes. Further analysis shows that the narrow bandwidth peak in the loss spectrum of the core mode is determined by the sensor dimensions contributed jointly by the thicknesses of the silver film, dielectric layer, and titanium dioxide film. Compared to the single-fiber structure, the optimized dual D-shape WCSPR sensor achieves a maximum wavelength sensitivity of 52,200 nm/RIU with a full-width at half-minimum (FWHM) of 9.47 nm and a figure of merit (FOM) of 346.6 RIU−1 in the analyte refractive index range of 1.32–1.42.

MXene-Assisted D-Shaped Photonic Crystal Fiber Probe with High Sensitivity for Detection of Tuberculosis

MXene-Assisted D-Shaped Photonic Crystal Fiber Probe with High Sensitivity for Detection of Tuberculosis

Fabricate a highly sensitive surface plasmon resonance optical fiber sensor based on a D-shape fiber coated with gold (Au) nano-layer

In this study, a D-shape fiber coated with a gold (Au) nano-layer is proposed as the basis for a highly sensitive surface plasmon resonance (SPR) optical fiber sensor that is used to detect the refractive index RI of the glucose solution, with the possibility of using this sensor as a biosensor. By variety side-polishing multimode fiber with different sensing lengths (1 cm, 1.5 cm, and 2 cm) and coating it with a thin layer of 50 nm gold film, the SPR D-shape fiber sensor was developed. The impacts of the sensing area and various residual fiber thicknesses are explored in order to acquire the optimal values of the SPR D-shape fiber sensor. Observations revealed that various concentrations of glucose, ranging from 1% to 9%, were tested on an SPR D-shape fiber sensor, with sensitivity growing to 3.101 au. RIU−1 and linearity reaching 98%. The sensor responded quickly to the refractive index from 1.334 to 1.346 RIU. The future of glucose sensors looks bright with gold-coated D-shaped fiber sensors, they may also work well with other factors like temperature or strain due to their excellent sensitivity, stability, and repeatability.

Optical mid-infrared modulator based on D-shaped photonic crystal fiber and GST phase changing material

Photonic crystal fibers (PCFs) have recently attracted compelling attention because of their numerous applications, particularly in the mid-infrared (mid-IR) wavelength region. In this paper, we have presented and analyzed mid-IR optical modulator based on phase-changing material (PCM) known as germanium-antimony-tellurium (GST) and D-shaped PCF. The modulation process can be performed as the GST material’s phase undergoes a transition between amorphous (on) and crystalline (off) states. To analyze the proposed design numerically, full vectorial finite element method (FVFEM) is employed. Further, we studied the light propagation through the suggested structure using 3D finite difference time domain (FDTD) method. The optical losses of the fundamental transverse electric (TE) mode supported by the reported structure in the two GST states are studied. The obtained extinction ratio (ER) of the proposed modulator approaches 302.61 dB, whereas the insertion loss (IL) is less than 0.00014 dB throughout the wavelength range from 3 to 5.8 μm at a device length (LD) of 0.2 mm. Therefore, the suggested modulator can be utilized in photonic integrated circuits that require high ER, very low IL, and large optical bandwidth.

Graphene/Au/MIP-Coated D-Shaped Optical Fiber–Based SPR Sensor for Ethanol Detection

Graphene/Au/MIP-Coated D-Shaped Optical Fiber–Based SPR Sensor for Ethanol Detection

A D-Shaped SPR-Based PCF Sensor with an Extremely High-Amplitude Sensitivity for Measuring the Refractive Index.

In this work, a new D-shaped photonic crystal fibre sensor structure based on surface plasmon resonance (SPR) is purposed for measurement of analyte refractive index (RI). In this design, a silica cylinder is polished into a D-shaped silica material structure with a flattened surface where two Au nanowires are coated. Some air holes are omitted to form the core mode region. With the implementation of gold nanowires and a core region for the exciting SPR effect with variate physical values, analyte RI can be measured with a wavelength coverage from 850 to 1350nm. The numerical simulation shows the maximum wavelength sensitivity of the purposed design achieves 19,600nm/RIU with an RI coverage from 1.37 to 1.42. Moreover, the sensor has a tremendous amplitude sensitivity and the maximum absolute value is about 2300RIU-1. Benefiting from these outstanding performance, the purposed structure can be given priority when it is applied in biomedical detecting and environmental assessment science.

Development and Analysis of Multifeature Approaches in SPR Sensor Development

This paper presents the development and signal analysis of surface plasmon resonance (SPR)-based sensors in D-shaped polymer optical fibers (POFs). A gold-palladium (Au-Pd) coating was applied to the D-shaped region to obtain the SPR signal in the transmitted spectrum of the POFs, where different samples were fabricated using the same methods and parameters. In this case, the transmitted spectra of three sets of samples were compared, which indicated variations in the SPR signature that can influence the sensors’ application and reproducibility. Then, the intensity of and wavelength shift in the SPR signals were analyzed as a function of the refractive index variation, where it was possible to observe differences in the sensors’ sensitivities and the linearity of the different samples. In this regard, additional features, namely the area below the curve and the peak amplitude of the fast Fourier transform (FFT) applied to the transmitted spectra, were used to enhance the sensors’ accuracy and precision. To verify the use of such additional features in the sensor analysis, an unsupervised approach based on k-means clustering was used considering a single dataset with the results of all the sensors. The results showed clustering with the number of different refractive indices tested, which motivated the use of these features (intensity, wavelength, area and FFT amplitude) in the refractive index assessment. In this context, random forest was the supervised algorithm with the smallest root mean squared error (RMSE) among the algorithms tested, where an RMSE of 0.0057 was obtained considering all the datasets. For the analysis of each sensor (considering the three sets of sensor samples), the mean RMSE using random forest applied to the multifeature approach returned relative errors below 9%, considering the entire tested range of refractive index variation.