Air Holes Of Photonic Crystal Fiber Research Articles

Highly sensitive methane gas sensor based on Au/UVCFS films coated D-shaped photonic crystal fiber

In recent years, the proportion of methane explosion accidents in coal mine production accidents is increasing. The important measure to avoid methane explosion accident is to do well in methane leakage detection. Some of the surface plasmon resonance (SPR) based photonic crystal fibers (PCFs) have been proposed to achieve the methane gas sensing. However, it is difficult to fill methane gas into the inner air holes in PCFs. In order to address this issue, a D-shaped PCF methane gas sensor based on SPR was proposed and investigated based on the finite element method in this paper. A side polished air hole in the D-shaped PCF was utilized as the substrates for depositing the gold film and methane gas sensitive film. The sensing area is in direct contact with the outside methane gas. Simulation results showed that the measurement sensitivity of methane gas reached 9.88 nm/% at the methane concentration of 0%–3.5% with a linearity of 99.8%. The influence of optical structure parameters on sensor performances were also discussed. The designed sensor is expected to be a candidate for methane gas leakage detection for its simplicity and feasibility.

Susceptible Plasmonic Photonic Crystal Fiber Sensor with Elliptical Air Holes and External-Flat Gold-Coated Surface

This paper proposes and analyzes a simple surface plasmon resonance (SPR)-based elliptical air hole photonic crystal fiber (PCF) sensor. The fiber structure comprises an analyte channel of the fiber surface coated with a gold layer on the flat surface and the fiber’s external surface. Numerical simulations are conducted using the finite element method (FEM) with an external sensing approach. We found that the thickness of plasmonic material (Au) is the most crucial factor that affects the full width at half maximum (FWHM) and confinement loss amplitude. We also demonstrated that the proposed elliptical air hole SPR-PCF is superior to circular air hole SPR-PCF in terms of confinement loss and FWHM. According to the wavelength interrogation technique, the simulation results show that the designed SPR-PCF sensor can attain a maximum sensitivity of 116,500 nm/RIU and a resolution of 8.58 × 10−7 RIU (RIU: refractive index unit) for the analyte RI of 1.395. We believe the proposed SPR-PCF sensor can be a potential candidate for biomolecular and biological analyte detection.

Research on novel variable air-hole photonic crystal fiber

Abstract A novel PCF (photonic crystal fiber) with variable air holes is designed to solve the problem that it is difficult to obtain flatted dispersion and low confinement losses simultaneously it can obtain flatted dispersion and low confinement losses by changing the size of air hole in the cladding. The structure of the optical fiber is analyzed by using FVFEM (full vector finite-element method) and APML (anisotropic perfectly matching layer) boundary conditions. The effective refractive index of the air hole at 1.55 μm is n 0 = 1, and that of quartz is set as 1.45,under these conditions, the simulation results show that the optical fiber has super-flat dispersion in the wavelength range of 1.25–1.78 μm, the dispersion varies ranges from 0 ± 0.68 (ps/nm km), and the confinement losses is less than 10−3 dBb/m.

Fully negative near-zero ultra-flat dispersion photonic crystal fibers in E+S+C+L band

We demonstrate a modified hexagonal three-layer air-hole photonic crystal fiber (PCF) which presents a good ability of dispersion management. The proposed PCF not only achieved an ultra-flattened all-negative dispersion characteristics of 0.15085 ps/(km·nm) fluctuation within the wavelength range of E+S+C+L wavelength band but also has been able to obtain other interesting features such as low confinement loss. Furthermore, the quadrilateral and octagonal structures are investigated to compare the superiority of different structures and analyze why we chose the hexagonal one.

Surface plasmon based fiber optic refractive index sensor

This paper has proposed a surface plasmon resonance-based photonic crystal fiber (PCF) sensor to detect even a small change in refractive index (RI) values of analytes. The impact on sensor performance by Bezier polygon core structure of the PCF and gold coating in an air hole have been carried out. The sensor resonance wavelength and the respective confinement loss are analyzed for various Bezier polygon parameters and for various gold coating thicknesses. Also, a comparison between gold filling and gold coating in an air hole of PCF have been undertaken to show the superiority of the gold coating in sensor performance. The promising sensor performance has been noted down above the analyte RI of about 1.3 with an upright sensitivity of about 7000 nm/RIU. This type of sensor is of great interest in medical and industrial applications.

A novel temperature insensitive refractive index sensor based on dual photonic crystal fiber

A novel dual photonic crystal fiber (DPCF) temperature insensitive refractive index sensor is proposed in this article. By sequentially splicing lead-in SMF (single mode fiber), PCF_1, PCF_2, and lead-out SMF constitute the Mach-Zehnder interferometer (MZI). The refractive index sensitivity (RIS) of the proposed sensor is improved by making an abrupt-taper on the fusion point of two PCFs. The proposed sensor is compared with a sensor without an abrupt-taper, the RIS value of the proposed sensor is increased by ∼1.9 times. The collapsed area of two photonic crystal fiber air holes is used as a beam splitter and combiner of Mach-Zehnder interferometer. Experimental analysis indicates that the RIS is 152.97 nm/RIU (1.330–1.383 RIU). Besides, the proposed sensor is independent of temperature and its sensitivity towards temperature is only -0.0045 nm/°C (30−80 °C). This sensor has the characteristics of relatively high sensitivity, ease of fabrication, and compact size.

Two Modes Excited SPR Sensor Employing Gold-Coated Photonic Crystal Fiber Based on Three-Layers Air-Holes

Ahighly sensitive refractive index (RI) biosensor based on three-layers air-holes photonic crystal fiber (PCF) with gold film on the outer edge of the fiber cladding is proposed. The properties of modes coupling between fundamental mode (odd mode), cladding mode (even mode) and surface plasmon polaritons (SPPs) mode were theoretically simulated, respectively. Meanwhile, the effects of gold film thickness and cladding air-hole diameter on the sensor performance are analyzed in detail. When the energy of odd and even modes couple strongest to SPP mode with the gold film is 50 nm, the maximum sensitivities of this PCF sensor are 8400nm/RIU (odd mode) and 8500nm/RIU (even mode), respectively under the RI of 1.41. Compared with the traditional optical fiber sensor, this PCF sensor has the advantages of wide and real-time detection, compact and high RI sensing responsivity, which has the potential to be used in the field of environment quality-detection and biochemistry sensing.

Magnetic field and temperature dual-parameter sensor based on magnetic fluid materials filled photonic crystal fiber.

A dual-parameter sensor based on a photonic crystal fiber (PCF) concatenated with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. Novel magnetic fluids (MF) with different concentration and surfactant are filled in the air holes of PCF. The magnetic field measurement property is only determined by PCF, while the temperature is co-determined by PCF and FBG. Experimental results show that the wavelength shift has a good linearity corresponding with temperature and magnetic field. Temperature and magnetic field sensitivity are proportional to concentration of MF and are affected by different surfactants. For PCF point, when polyethylene glycol is used as a surfactant and the magnetic fluid concentration is equal to 0.15, the highest magnetic field sensitivity is up to 924.63 pm/mT. The proposed sensor has a high sensitivity as well as cross-sensitivity resistance, which provides a promising candidate for dual-channel filtering or multi-parameter measurement applications.

A compact electro-absorption modulator based on graphene photonic crystal fiber**Project supported by the National Natural Science Foundation of China (Grant Nos. 61575170 and 61675176), the Key Basic Research Program of Hebei Province, China (Grant No. 16961701D), and the “Xin Rui Gong Cheng” Talent Project of Yanshan University.

A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene–light interaction is obtained. Moreover, the switch on–off point of the modulator is unchangeable, which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode, 3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.

Multi-channel few-mode multicore fiber based surface plasmon resonance biosensor with open air-hole

Based on the structural characteristics of the few-mode multicore fiber (FM-MCF), a multi-channel FM-MCF surface plasmon resonance (SPR) biosensor with open air-hole is presented. Due to the air-hole distribution of the FM-MCF, the six outer air-holes naturally become open air-holes, i.e. groove sensing channels, fabricated by chemical etching. Then, compared with D-shape structure, tapered structure of fiber and air-hole of photonic crystal fiber (PCF), the open groove structure is easy to accommodate the liquid analyte. In order to obtain better sensing performance, a sensing model of the presented FM-MCF SPR biosensor with sensitive dielectric layer is established and numerical simulations are performed using the finite element method. In the simulations, the effect of core-hole distance, coating thickness, sensing dielectrics, transmission modes in optical fiber on the sensing performance as well as the role of multi-channel are analyzed. The simulation results show that when the air-hole is tangent to the core (<i>d</i> = 0 μm), the FM-MCF SPR biosensor has the better performance because the core-hole distance <i>d</i> determines the leakage intensity of the evanescent wave. As the evanescent field excited by high-order mode (LP<sub>11ax</sub> mode) is stronger than that by fundamental mode (LP<sub>01x</sub> mode), the performance of biosensors for SPR excitation by using high-order mode is better than by using fundamental mode. Meanwhile when the coating thickness of gold, silver and indium tin oxides (ITOs) is 40 nm, 30 nm and 100 nm respectively, the FWHM of loss spectrum reaches a minimum value, which means that the presented biosensor has the better performance in this sense. For the case of different sensing dielectrics, it is observed that the resonance wavelength of gold and silver film are in the visible wavelength range, while the ITO is at near-infrared wavelength. Then it is useful for our biosensor to simultaneously detect many liquid analytes in one SPR transmittance spectrum. In addition, the calculation results also show that when one of the groove channels is coated with 100 nm ITO for the LP<sub>11ax</sub> mode, the FM-MCF SPR biosensor has a highest sensitivity of 20824.66 nm/RIU and refractive index (RI) resolution is 4.8 × 10<sup>–6</sup> RIU with the surrounding RI changing from 1.33 to 1.39, in which the RI of bovine serum albumin (BSA) solution, human Immunoglobulin G and C-reactive protein can be detected. Moreover, when the outer groove channels of our biosensor are coated with gold, silver and ITO film with different thickness, many biological liquid analytes can be detected separately or the same biological liquid analyte can be detected jointly, which reveals that the control flexibility of the groove sensing channel and the diversity of the detection analytes .

Synthesis of photonic crystal fiber based on graphene directly grown on air-hole by chemical vapor deposition

The integration of fiber with graphene has greatly expanded the two-dimensional functional materials in the field of photonics research. However, the growth method by using chemical vapor deposition with metal catalytic substrateis limited to the fabrication of a graphene-fiber composite due to inevitably transferring graphene flakes onto the optical fiber surface. In order to fully achieve the interaction between light and graphene material, optical fibers have to be treated with special structure, which greatly damages the fiber structure, resulting in inefficient and harmful manufacturing strategy for the mass production. In this paper, a graphene-photonic crystal fiber (G-PCF) composite is prepared by atmospheric chemical vapor deposition (APCVD), which can directly grow monolayer and multi-layer graphene into the air-hole of photonic crystal fiber. Furthermore, we randomly break a G-PCF and then conduct an electron microscope (SEM) test at the fractured section. It is obvious that a tube-like graphene protruding out of one hole in the fractured area of the G-PCF is observed, thus further demonstrating that a monolayer graphene is grown on the inner hole walls of the PCF as shown in <xref ref-type="fig" rid="Figure2">Fig. 2</xref>. By changing the process parameters such as growth temperature, duration and gas flow rate of carbon source, the law of the influence of different parameters on the graphene layers is explored. In addition, the uniformity of graphene and defects in the graphene-photonic crystal fiber(G-PCF) are experimentally analyzed. As illustrated in <xref ref-type="fig" rid="Figure7">Fig. 7</xref>, a 4-cm-long uniform graphene-photonic crystal fiber sample is achieved by controlling the gas flow rate, growth time and the growth temperature. The APCVD method of directly growing graphene onto the inner hole walls of the PCF is simple and effective. The flexible structure and optical control enable the G-PCF to have great potential applications in all-optical devices and photonics. The development of high-quality graphene synthesis and opto-electronics technology ensures its compatibility with the integrated electronics platform and existing optical fiber systems. Moreover, our results will pave the way for 2<i>D</i> materials and optical fiber applications, providing a new idea for the application of graphene to the integration of all-optical fibers.

Design and Simulation of Surface Plasmon Resonance Sensors for Environmental Monitoring

In this work a Surface Plasmon Resonance (SPR) sensor based on Photonic Crystal Fiber (PCF) infiltrated with water samples has been proposed. To accurate detection of the sample properties, gold is used as plasmonic material. The air holes of PCF has been infiltrated with water samples, the optical properties of these samples has been taken from samples collected from Al-Qadisiya and Wathba lab. (east Tigris, Wathba, and Al-Rasheed) water projects at Baghdad- Iraq. Finite Element Method (FEM) has been used to study the sensor performance and fiber properties. From the numerical investigation we get maximum sensitivity circa 164.3 nm/RIU in the sensing range of 1.33 (of STD water) to 1.3431 (of river sample). The proposed sensor could be developed to detect f various high refractive index (RI) chemicals like the heavy metals in water.

Folded cladding porous shaped photonic crystal fiber with high sensitivity in optical sensing applications: Design and analysis

A micro structure folded cladding porous shaped with circular air hole photonic crystal fiber (FP-PCF) is proposed and numerically investigated in a broader wavelength range from 1.4µm to 1.64µm (E+S+C+L+U) for chemical sensing purposes. Employing finite element method (FEM) with anisotropic perfectly matched layer (PML) various properties of the proposed FP-PCF are numerically inquired. Filling the hole of core with aqueous analyte ethanol (n=1.354) and tuning different geometric parameters of the fiber, the sensitivity order of 64.19% and the confinement loss of 2.07×10-5 dB/m are attained at 1.48µm wavelength in S band. The investigated numerical simulation result strongly focuses on sensing purposes; because this fiber attained higher sensitivity with lower confinement loss over the operating wavelength. Measuring time of sensitivity, simultaneously confinement loss also inquired. It reflects that confinement loss is highly dependable on PML depth but not for sensitivity. Beside above properties numerical aperture (NA), nonlinearity, and effective area are also computed. This FP-PCF also performed as sensor for other alcohol series (methanol, propanol, butanol, pentanol). Optimized FP-PCF shows higher sensitivity and low confinement loss carrying high impact in the area of chemical as well as gas sensing purposes. Surely it is clear that install such type of sensor will flourish technology massively.

Silicate Glass Hybrid Fiber With All-Normal Dispersion for Coherent Supercontinuum

Supercontinuum generation (SCG) in an all-normal dispersion fiber possesses a high degree of coherence, which has several applications. Traditional air-hole photonic crystal fibers have some limitations for achieving such light emission. In this paper, hybrid fibers with a silica glass cladding and a yttria–alumino–silicate glass core, designed for flat coherent SCG, were fabricated. The core material features a high nonlinearity and a large refractive index difference with silica for dispersion engineering. We achieved a flat normal dispersion in this hybrid fiber. Flat supercontinuums (SCs) were generated under different pump conditions. Numerical studies coincided well with the experimental results. The simulated results indicate that the spectrum can extend to more than one octave with high input power. The generated SC spectrum has good coherence.

PCF Based Sensor with High Sensitivity, High Birefringence and Low Confinement Losses for Liquid Analyte Sensing Applications

In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped V-PCF and horizontally-shaped H-PCF. The full vectorial Finite Element Method (FEM) simulations performed to examine the sensitivity, the confinement losses, the effective refractive index and the modal birefringence features of the proposed elliptical air hole PCF structures. We show that the proposed PCF structures exhibit high relative sensitivity, high birefringence and low confinement losses simultaneously for various analytes.

Mode converter based on dual-core all-solid photonic bandgap fiber

In this paper, we present a mode-selective coupler based on a dual-core all-solid photonic bandgap fiber (AS-PBGF). Because they are all-solid, AS-PBGF-based mode converters are easier to splice to other fibers than those based on air-hole photonic crystal fibers. Mode conversions between the LP01 and LP11 modes, LP01 and LP21 modes, and LP01 and LP02 modes are obtained at the wavelength λ=1550 nm. The 3 dB wavelength bandwidth of these mode converters are 47.8, 20.3, and 20.3 nm, respectively.

Diamond unit cell photonic crystal fiber with high birefringence and low confinement loss based on circular air holes.

We propose a novel photonic crystal fiber (PCF) design with high birefringence and low confinement loss based on a diamond unit cell. Unit cell is a degree of freedom of PCF design, and highly asymmetric diamond unit cell can deliver both high birefringence and low confinement loss. In our fiber design, each diamond unit cell consists of two different sizes of circular air holes in a conventional hexagonal lattice, which can enhance the confinement loss with increased birefringence and can overcome the previous fabrication challenges of elliptic air hole PCFs due to the all-circular air hole structure. The optimized design shows high birefringence of 6×10(-3) over S, C, and L bands while maintaining low confinement loss.

Experimental measurement of the temperature-birefringence characteristics of birefringent photonic crystal fiber filled with ethanol

The birefringence value of the birefringent photonic crystal fiber (PCF) is not sensitive to the change of temperature, while the refractive index of ethanol will be changed with the varied temperature. So if the air-holes of PCF are filled with ethanol, the birefringence value will surely change along with the varied temperature, which can be used as a sensing principle to measure temperature. In this paper, a method called End Face Reflection of the optical fiber was used to measure the refractive index against the change of temperature. The experimental results indicated that, on the condition of the incident wavelength of 1550nm, the refractive index of ethanol changed from 1.3691 to 1.3602 within the temperature ranging from 24.5°C to 44.5°C. The birefringence value of the filled PCF changed from 1.8900e-04 to 2.1500e-04. That is to say, the temperature sensitivity coefficient could reach 10e-6 order of magnitude.

Design of a Concentration Sensor Based on Photonic Crystal Fiber Placed between Two Single Mode Fibers

We demonstrate the use of photonic crystal fiber (PCF) joined in between two single mode fibers (SMF) as a concentration sensor. To realize this, one micrometer length PCF of hexagonal lattice is sandwiched between two SMF having one micrometer length each. To maximize the coupling between SMF and PCF, the core diameters are made equal. Then the output from a given input through this structure is analyzed with respect to different concentrations in the air holes of PCF using Finite Difference Time Domain (FDTD) method. It is found that the variation of electric field intensity at the output is linear with respect to concentration of alcohol.

Magneto-optical fiber sensor based on bandgap effect of photonic crystal fiber infiltrated with magnetic fluid

A magnetic field sensor based on combination of the magnetic fluid and the tunable photonic bandgap effect of photonic crystal fiber is proposed. The magnetic fluid with higher refractive index (>1.45) is prepared and filled into the air-holes of photonic crystal fiber to convert the index guiding fiber into photonic bandgap fiber. The proposed sensor takes full advantage of the ultrahigh sensitivity characteristic of photonic bandgap fiber and achieves a high sensitivity and resolution of 1.56 nm/Oe and 0.0064 Oe, respectively, which are 2-3 orders of magnitude better than other sensors based on magnetic fluid.