Fiber Refractive Index Sensor Research Articles

Refractive index sensing characteristics of PCF-SPR based on dual-plasmon materials

Abstract In this paper, a photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR) with dual plasmonic materials (indium tin oxide and gold) is proposed. We innovatively designed a dual-core PCF structure and pore arrangement effectively enhancing the coupling effect. Using two different plasma materials, phase matching is achieved at two different wavelengths for the evanescent and surface plasmon waves, resulting in dual resonance peaks. The refractive index sensing is accomplished by measuring the dual-peak resonance shift, which expands the detection wavelength and RI detection ranges. The sensor can detect analytes with refractive indices ranging from 1.32 to 1.43 at wavelengths between 0.4 um and 1.4 um. We optimized the photonic crystal fiber structure and studied the sensing performance of the sensor, improving its sensitivity. Simulation results indicate that the designed PCF sensor exhibits outstanding maximum dual-peak shift sensitivity (DPSS), reaching up to 28,000 RIU-1, along with maximum amplitude sensitivity (AS) and wavelength sensitivity (WS) of 18,500 RIU-1 and 34,500 RIU-1, respectively, in the direction of y-polarization. Furthermore, the sensor achieves high resolution, and the figure of merit (FOM) values can reach up to 5.134×10-7 and 2758. Consequently, the proposed sensor can provide high-precision and extensive-range measurements of solution refractive indices within the visible and infrared light spectrum, and it holds potential application prospects in numerous fields, such as food safety testing and chemical substance detection.

Optimization of highly sensitive three-layer photonic crystal fiber sensor based on plasmonic

In this work, a photonic crystal fiber (PCF) refractive index (RI) sensor has been designed and optimized. The RIs range covered by the sensor is from 1.38 to 1.41. The proposed optical sensor has three layers of air holes with 24, 12 and 6 holes in each layer. The geometry parameters of the proposed sensor (the radius of the air holes and the thickness of the plasmonic layer) have been optimized using the Nelder-Mead algorithm and the FEM numerical with the objective of achieving the highest sensitivity. To achieve an optimized structure with minimal sensitivity to fabrication errors, the rotation angle of the hole layers has been analyzed. The results indicate that, due to the specific geometry of the proposed structure, variations in the rotation angle and displacement of the air holes have no significant impact on the outcomes. The results also indicate that the sensor’s maximum amplitude sensitivity (AS), maximum wavelength sensitivity (WS), and figure of merit (FOM) are 10000 (RIU−1), 23000 (nm/RIU) and 131 (RIU−1) respectively. The optimized design provides high sensitivity, a wide diagnostic range for the detection of the analytes’ RIs, and the advantages of a gold plasmonic layer, ensuring high stability in biological environments. This combination results in enhanced performance of the sensor for various applications particularly in biosensing and medical fields. The designed structural geometry also eliminates the effects of tolerances in manufacturing processes which makes the proposed PCF device a very efficient sensor.

A fiber optic refractive index sensor with temperature compensation based on cascaded Mach-Zehnder interference and Intermodal interference

Optical fiber refractive index (RI) sensor with temperature (T) compensation has important application values in biomedicine and environmental monitoring. In order to solve the problem that the detection accuracy of liquid RI is affected by T in practical applications, a T-compensated RI fiber sensor based on cascaded Mach-Zehnder interference (MZI) and multimode interference (IMI) is proposed in this paper. Experimental results showed the proposed sensor achieved a sensitivity of 797.41 nm/RIU for the measurement of RI in the range of 1.3333–1.3640, and a sensitivity of 0.120 nm/°C for the measurement of T in the range of 0–60 °C. The resolution (R) of RI and T measurements reached 2.5 × 10−5 RIU and 0.167 °C, respectively. The detection limits (DL) of RI and T measurements are 3.135 × 10−8 RIU and 1.392 °C, respectively. A matrix is obtained to demodulate the cross-sensitivity in RI and T measurements. The proposed sensor shows the advantages of simple structure, low hysteresis, and good stability.

Simulation analysis of a photonic crystal fiber refractive index sensor based on a double-layer film structure and surface plasmon resonance technology

A photonic crystal fiber surface plasmon resonance sensor based on a double-layer membrane structure is designed and analyzed. In the simple sensing structure with only one air hole size, TiO2 and Au layers with specific thicknesses are sequentially coated on the optical fiber to form a double-layer structure. The sensing characteristics of the double-layer membrane structure are studied by the finite element method. Compared to the single-layer membrane structure, the double-layer membrane sensor has significant sensing properties such as a better wavelength sensitivity and a smaller full width at half maximum in the loss spectrum. In the refractive index range between 1.37 and 1.43, the maximum wavelength sensitivity and average wavelength sensitivity of the sensor are 19,900 nm/RIU and 7417 nm/RIU, respectively, and the resolution can be up to 5.03×10−6RIU. The proposed photonic crystal fiber optic sensor achieves high performance with a simpler sensing structure than previous photonic crystal fiber optic sensors, and eliminates the step of polishing, which will greatly reduce the difficulty of actual fabrication and the error due to uneven polishing. The results show that the photonic crystal fiber optic sensor with a double-layer membrane structure has excellent performance. Due to its high sensitivity and resolution, it has great potential for applications in environmental monitoring, biosensing and chemical sensing.

Gold-coated D-shaped photonic crystal fiber refractive index sensor with a wide detection range and large manufacturing tolerance

A D-shaped photonic crystal fiber refractive index (RI) sensor is designed, and its performance is analyzed using the finite element method (FEM). A gold film is coated on the D-shaped surface of the fiber as a plasmonic material for surface plasmon resonance sensing. The U-shaped arrangement of holes of the same size in the fiber structure enhances the coupling resonance between the core mode and the surface plasmon polariton mode. Numerical results show that the RI range of the sensor is 1.20–1.40, the maximum wavelength sensitivity is 16008.98 nm/RIU, and the detection width is up to 0.2 RIU. In addition, this study analyzes the manufacturing tolerance for the sizes of the air holes. The results show that the manufacturing tolerance for the three types of air holes is as high as 25%, 11.1%, and 10.2% when h is 40µm. These findings lay the foundation for the mass production of sensors. The above results indicate that the sensor has remarkable advantages such as enhanced sensitivity, wide measurement range, and exceptional manufacturing stability, and has promising applications in the fields of bio-detection, drug supply detection, and water pollution control.

A novel D-shaped photonic crystal fiber refractive index sensor based on surface plasmon resonance effect

A novel D-shaped photonic crystal fiber refractive index sensor based on surface plasmon resonance effect

D-type photonic crystal fiber refractive index sensor based on Bloch surface waves

Bioassays are important in health assessment, disease diagnosis, treatment monitoring, disease prevention, and environmental monitoring to provide better health management and quality of life for individuals and society. A D-type photonic crystal fiber optic sensor based on Bloch surface waves is proposed for biological detection within an ultra-wide refractive index. The designed D-type fiber was side-polished and alternately deposited with one-dimensional photonic crystals (1DPCs) on the polished side, consisting of a set of TiO2 and SiO2 alternating media with moderate refractive index differences. The designed PCF consists of symmetric air holes and polished structures. The structural parameters of this sensor are also analyzed and discussed in order to obtain better detection performance. The designed Bloch surface wave D-type photonic crystal fiber optic sensor has a maximum refractive index sensitivity of 5400 nm/RIU and a maximum amplitude sensitivity of 513.00RIU−1. The sensor also has a resolution of 1.85×10−5RIU and an excellent maximum quality factor (FOM) of 222.43RIU−1. These results show a higher figure of merit (FOM) than conventional methods, resulting in increased sensitivity and accuracy. The proposed sensor can detect the RI of unspecified analytes between 1.20 and 1.50, allowing for the analysis of many different types of analytes, such as viruses, blood plasma, cancer cells, sugars, proteins, DNA/RNA, and many more.

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

Advances in dispersion turning point enhanced ultrasensitive optical fiber refractive index sensors

Optical fiber sensor operating at the dispersion turning point (DTP) has become a promising building block for future development in biosensing application due to its ultrahigh sensitivity. In this paper, we comprehensively review the fundamentals of various optical fiber sensors under the turning point condition, together with the basic definition, classification, design, fabrication and applications. Three main methods for DTP implementation are introduced and highlighted: i) phase matching condition in long period grating, ii) refractive index (RI) matching to the effective refractive index of the waveguide in modal interferometer, and iii) mode coupling via diameter regulation in modal interferometer, optical microfiber coupler and polarization interferometer. The aim here is to provide reliable and effective methods to achieve the superior performance on turning point-enhanced optical fiber RI sensors, accelerating the development of transduction technology for the research of novel biomedical sensors.

Experimental study on ultra-high sensitivity gold-based SPR sensor for refractive index and temperature measurement

We have experimentally demonstrated an ultra-high sensitivity gold-based fiber refractive index (RI) sensor whose main structure is composed of multimode fiber (MMF) and photonic crystal fiber (PCF). The gold film is deposited on V-shaped PCF by magnetron sputtering, and sensing experiments are performed based on the principle of surface plasmon resonance (SPR). Numerical simulation results indicate that the cladding mode of the V-shaped PCF is more capable of stimulating the SPR effect than the core mode. The experimental results show that the RI measurement range of the sensor is 1.333–1.421, with a maximum sensitivity of 10015 nm/RIU. In addition to RI sensing, sensing probes can be coated with polydimethylsiloxane (PDMS) on a gold film for temperature sensing. For temperature detection, the range is from 10 to 100 °C and the maximum sensitivity is 3.5 nm/℃. Besides high sensitivity in RI measurement, the proposed sensor also has good sensing performance in temperature sensing. With the advantages of high sensitivity, good stability, and easy preparation, this sensor has become an important reference in the field of high-performance sensing.

D-type photonic crystal fiber refractive index sensor with ultra-high fabrication stability and ultra-wide detection range

D-type photonic crystal fiber refractive index sensor with ultra-high fabrication stability and ultra-wide detection range

Design and analysis of surface-plasmon-resonance-based dual-cladding micro-structured fiber temperature and refractive index sensor

Combining the surface plasmon resonance(SPR) effect and the characteristics of dual-cladding micro-structured fiber(DC-MF), this study presents the design and analysis of a temperature and refractive index sensor. The performance of the sensor is analyzed by using the full-vector finite element method, and the structure parameters of the DC-MF and the thickness of the plasmonic material (ITO film), is optimized to achieve high sensitivity measurements of temperature and refractive index. Theoretical analysis results indicate that its maximal temperature and refractive index sensitivity can reach to 25.4 nm/°C and 46559.8 nm/RIU in −40 °C to −40 °C. Its average temperature and refractive index sensitivity is 22.53 nm/°C and 38292.3 nm/RIU in the temperature range from −40 °C to 0 °C, and the value is 7.03 nm/°C and 12591.7 nm/RIU in the temperature range from 0 °C to 40 °C. Besides, its operating wavelength shifts toward a long wavelength region (about 1.05 μm–2.25 μm) as the refractive index of analyte increases from 1.424 to 1.471.

High Resolution and Sensitivity Negative Curvature Hollow Core Fiber Refractive Index Sensor Based on LSPR

High Resolution and Sensitivity Negative Curvature Hollow Core Fiber Refractive Index Sensor Based on LSPR

Design of a New Type of In-Hole Gold-Coated High-Performance Quasi-PCF Sensor Enhanced with Surface Plasmon Resonance

With the development of aerospace, deep-sea exploration and other technologies, the demand for anti-electromagnetic, high-sensitivity and miniaturized sensors is increasingly urgent. In this paper, a model of a quasi-photonic crystal fiber (Q-PCF) refractive index (RI) sensor enhanced with surface plasmon resonance (SPR) is proposed. A stable gold film with a significant SPR effect is applied to the two identically sized and oppositely positioned air holes of the proposed sensor, and all air holes are filled with analyte. A detailed analysis of the mode characteristics, structural parameters and RI sensing performance of the sensor has been carried out using the finite element method. It has been shown that the maximum sensitivity (S) is 4977.59 nm/RIU in the RI range of 1.35–1.40, corresponding to a resolution (R) of 2.01 × 10−5 RIU and a figure of merit (FOM) of 160.36 RIU−1. The proposed Q-PCF sensor has unique fabrication advantages and outstanding sensing properties, providing a new idea for biosensing, complex environment monitoring and long-range measurement, and is of great practical value in the field of highly integrated sensing.

Distributed Refractive Index Sensing Based on Etched Ge-Doped SMF in Optical Frequency Domain Reflectometry.

A distributed optical fiber refractive index sensor based on etched Ge-doped SMF in optical frequency domain reflection (OFDR) was proposed and demonstrated. The etched Ge-doped SMF was obtained by only using wet-etching, i.e., hydrofluoric acid solution. The distributed refractive index sensing is achieved by measuring the spectral shift of the local RBS spectra using OFDR. The sensing length of 10 cm and the spatial resolution of 5.25 mm are achieved in the experiment. The refractive index sensing range is as wide as 1.33-1.44 refractive index units (RIU), where the average sensitivity was about 757 GHz/RIU. Moreover, the maximum sensitivity of 2396.9 GHZ/RIU is obtained between 1.43 and 1.44 RIU.

High sensitivity photonic crystal fiber temperature and refractive index sensor based on surface plasmon resonance

High sensitivity photonic crystal fiber temperature and refractive index sensor based on surface plasmon resonance

Ultrasensitive refractive index fiber sensor based on high-order harmonic Vernier effect and a cascaded FPI.

This paper proposes and demonstrates an ultrasensitive refractive index (RI) sensor based on harmonic Vernier effect (HEV) and a cascaded Fabry-Perot interferometer (FPI). The sensor is fabricated by sandwiching a hollow-core fiber (HCF) segment between a lead-in single-mode fiber (SMF) pigtail and a reflection SMF segment with an offset of 37 µm between two fiber centers to form a cascaded FPI structure, where the HCF is the sensing FPI, and the reflection SMF is the reference FPI. To excite the HEV, the optical path of the reference FPI must be multiple times (>1) that of the sensing FPI. Several sensors have been made to conduct RI measurements of gas and liquid. The sensor's ultrahigh RI sensitivity of up to ∼378000 nm/RIU can be achieved by reducing the detuning ratio of the optical path and increasing the harmonic order. This paper also proved that the proposed sensor with a harmonic order of up to 12 can increase the fabricated tolerances while achieving high sensitivity. The large fabrication tolerances greatly increase the manufacturing repeatability, reduce production costs, and make it easier to achieve high sensitivity. In addition, the proposed RI sensor has advantages of ultrahigh sensitivity, compactness, low production cost (large fabrication tolerances), and capability to detect gas and liquid samples. This sensor has promising potentials for biochemical sensing, gas or liquid concentration sensing, and environmental monitoring.

Design and numerical investigation of a dual-core photonic crystal fiber refractive index sensor for cancer cells detection

Design and numerical investigation of a dual-core photonic crystal fiber refractive index sensor for cancer cells detection

Portable Multihole Plastic Optical Fiber Sensor for Liquid-Level and Refractive Index Monitoring

In this article, we report a low-cost method to fabricate plastic optical fiber (POF) liquid-level and refractive index (RI) sensors integrated with smartphones by molds and drilling microholes in side-growing POFs (SGPOFs) with high-temperature metal wire. These sensors can be used for real-time liquid-level and RI monitoring, especially under situations requiring portability and illumination. When the liquid level changes, the change of the RI around the microholes leads to a change in the light intensity transmitted in the fiber, enabling us to measure the liquid level and RI. Utilizing one sensor with six holes (0.45 mm radius and 15 mm spacing) in 2.0-mm SGPOF, the results of level and RI measuring are in good agreement with the theory. The liquid-level measurement of the sensor is carried out for water with an RI of 1.333, the level sensitivity is 0.29%/cm ± 0.02%/cm. In the RI measurement, the RI sensitivity of the sensor is −22.8%/RIU ± 0.6%/RIU in the measurement range from 1.333 to 1.475.

Refractive index sensor based on a gradually hot-pressed flatted plastic optical fiber

This paper proposes a gradually hot-pressure plastic optical fiber (POF) refractive index (RI) sensor with a flatted structure to detect the glucose concentration, and experimentally investigates the performance of RI sensor with straight and micro-bending POFs. The sensor is fabricated by a temperature-controllable metal rod to form the hot-pressed end face of POF which can increase signal-to-noise ratio (SNR) of the sensor. The experimental results show that the proposed sensor, utilizing a flatted structure POF with thickness of 0.5 mm and diameter of 0.4 cm, achieves maximum intensity sensitivity of up to 1748.91 %/RIU and resolution of up to 5.97 × 10−4 RIU in the RI range of 1.33 to 1.382. Furthermore, its simple design and manufacturing process shows potential for application, especially in biochemistry and environmental safety.