Parameters Of Photonic Crystal Fiber Research Articles

Comparative study of different fiber materials based PCF for enhancing medical imaging quality

The image's quality is a crucial consideration in medical imaging, therefore selecting a fiber that offers more benefits is important. The primary objective of this work is to explore the imperative applications of Photonic Crystal Fiber (PCF) in medical imaging. Numerical studies utilizing the finite element method and a normal mesh have been performed on the proposed PCF with several different types of fiber materials in the core and background. More broadly in terms of wavelength, from 0.5 μm to 1.6 μm, some of the optical parameters investigated, including confinement loss, nonlinearity, effective area, and numerical aperture (NA). Changing PCF’s background material from BK7, fused silica, or ZBLAN has resulted in a shift in the parameters. Here, BK7 is discovered to be a promising possibility in medical imaging, and a thorough comparative analysis of PCF parameters has been performed. The comparison reveals that at an optical wavelength of 0.5 μm, the proposed PCF with BK7 exhibits strong nonlinearity of 119 W−1Km−1, low confinement loss of 2.97 × 10−12 dB/m, a numerical aperture of 0.15, along with a very low effective area of 4.18 × 10−12 m2. It is therefore anticipated that the suggested PCF with BK7 will be more suitable for the imaging application.

Coupling of laser diode with cylindrical microlens fabricated on the tip of single-mode photonic crystal fiber: prediction of coupling optics by ABCD matrix

Abstract We report the theoretical prediction of the coupling optics involving a laser diode and photonic crystal fiber which contains on its tip cylindrical microlens. The analysis is based on relevant ABCD matrix formalism. Though photonic crystal fiber has very large single-mode region, we carry on the investigation for two commonly used wavelengths such as 1.3 µm and 1.5 µm. For the particular kind of photonic crystal having specific value of air filling ratio and hole pitch, we have optimized the distance of laser diode from the microlens in order to get maximum value of coupling efficiency for each value of radius of cylindrical microlens. Incidentally, we have got here maximum coupling efficiency to the extent of 86.99 % at the wavelength 1.3 µm when the radius of the cylindrical microlens is 8.5 µm and effective spot size of the fiber is 4.433909 µm. Further, the maximum efficiency becomes 91.78 % at 1.3 µm when the radius of the cylindrical microlens is 4.0 µm and effective spot size of the fiber is 1.859907 µm. It has been shown that wavelength 1.5 µm is not so coupling efficient like 1.3 µm. Moreover, it has been shown that with same set of relevant parameters, PCF is more coupling efficient compared to ordinary graded index fiber. Thus the present work generates scope for varying different photonic crystal fiber parameters and the wavelengths of source as well for enhancing the coupling efficiency. Accordingly, the present analysis will be extremely helpful for design of efficient coupler of this kind.

SPR Sensor Based on a Concave Photonic Crystal Fiber Structure with MoS2/Au Layers.

We propose a surface plasmon resonance (SPR) sensor based on the concave photonic crystal fiber (PCF) coated with molybdenum disulfide (MoS2) and Au layers, which can detect the refractive index (RI) of the analyte. The finite element method (FEM) was used to verify our design, and the loss spectra of the fundamental mode are calculated. Compared with the SPR sensor with only a Au layer, the wavelength sensitivity can be improved by from 3700 to 4400 nm/RIU. Our proposed sensor works in near-infrared band and has a wide RI range from 1.19 to 1.40. The influences of the geometrical parameters of PCF and the thicknesses of Au and MoS2 layers on the loss spectra are discussed in detail, and the maximum wavelength sensitivity of 5100 nm/RIU can be achieved. Meanwhile, a high resolution of 1.96 × 10-5 RIU and the largest FOM of 29.143 can be obtained. It is believed that our findings show the sensor's excellent potential in medical testing, unknown biological detection, environmental monitoring and organic chemical detection.

Ultra-high sensitive refractive index sensor based on D-shaped photonic crystal fiber with graphene-coated Ag-grating

In this paper, an ultra-high sensitive plasmonic sensor is theoretically proposed for refractive index based on D-shaped photonic crystal fiber (PCF) with graphene-coated Ag-grating in mid-infrared region. Surface plasmon polariton at the metal/dielectric interface can be effectively excited by the fundamental guiding mode, leading to the surrounding medium-dependent loss spectrum. This metallic-grating PCF sensor exhibits a maximum sensitivity of 18612 nm/RIU with a detection resolution of 4.16 × 10−6 RIU in the index range from 1.33 to 1.395. Dependences of loss spectrum on the PCF parameters (air hole diameter and lattice constant) and the grating structure (grating thickness, period and width) are systematically analyzed. Moreover, the influence of the material parameters on the sensor performance is also investigated in term of graphene-layer number and the thickness of Ag layer. The compact design not only has great potentials in the applications of liquid detection, but also offers a guidance in the engineering of the metallic-grating fiber sensor.

Design of hexagonal chalcogenide photonic crystal fiber with ultra-flattened dispersion in mid-infrared wavelength spectrum

In the last few decades, silica-based photonic crystal fibers (PCFs) have been the subject of extensive research. Traditional silica-based PCFs, however, experience considerable propagation loss when used beyond 3000 nm. On the other hand, soft glasses, notably tellurite, fluoride, and chalcogenide glasses, offer exceptional optical transparency in the mid-IR wavelength region and are a desirable replacement for silica in MIR applications. A comprehensive investigation of chromatic dispersion properties in the hexagonal chalcogenide photonic crystal fibers is presented. The dependency of fiber dispersion on the structural parameters of photonic crystal fibers is thoroughly described in this study. Utilizing the interaction between material and geometrical dispersion, we were able to develop a well-defined framework for making specific predefined dispersion curves. In the mid-infrared wavelength spectrum, we are concerned with flattened, if not ultra-flattened, dispersion behaviors. In the wavelength range of 3500–6500 nm, the hexagonal chalcogenide microstructured fiber was engineered to achieve a typical dispersion profile flattened to within −3.41 to 9.5 ps/[nm–km] for the six-ring structure and −3.91 to 8.17 ps/[nm–km] for the four-ring structure. This proposed chalcogenide PCF can be used for soliton generation, gas sensing, biomedical imaging, supercontinuum generation, and long-distance high-speed communication applications in the mid-infrared wavelength range due to its nearly zero ultra-flattened dispersion characteristics.

Prediction of 12 Photonic Crystal Fiber Optical Properties Using MLP in Deep Learning

In this letter, we proposed the use of feed-forward multilayer perceptron in deep learning-based artificial neural network (ANN) to accurately predict 12 optical parameters of silica-based photonic crystal fiber (PCF) within milliseconds using 6 input parameters. The optimized ANN has 3 hidden layers and each layer has 50 neurons. The PCF has several hexagonal-shaped layers with circular air holes, and it uses silica as the cladding and FK51A glass as the core. The PCF parameters that have been successfully predicted include birefringence, chromatic dispersion, effective area, effective refractive index, nonlinear coefficient, numerical aperture, power fraction, relative sensitivity, V-parameter, and loss profiles such as confinement loss, effective material loss, and scattering loss. The prediction has high accuracy with a loss of only 0.00567 and a learning rate of 0.0001. 7-fold validation and batching are used to increase scalability during validation. The proposed ANN is over 99.9% faster than conventional numerical simulation approaches.

Deep Learning Based Data Augmentation and Behavior Prediction of Photonic Crystal Fiber Temperature Sensor

A photonic crystal fiber (PCF) structure which offers exceptional research prospects to design sensors is eccentrically found applicable in wide variety of fields and thus have prompted a lot of interest among researchers. However, intending to determine PCF design configuration producing desired optical response for worthwhile application forcefully necessitates investigating vast search space with suitable topological structure variants. Moreover, the existing Finite Element Method (FEM) based numerical simulation software demands intensively long computation time for each set of design parameters with quite several repetitions and is a challenging task with reduced computational complexity. In this regard, use of Deep Neural Networks (DNN) paves way to predict the outcome in less time. One of the most significant challenges encountered while training a neural network is to generate an extensive data set. With the motive of compensating for the same issue, we propose the use of Autoencoder (AE) network to achieve data augmentation. In this research, a pioneering approach to predict optical parameters of PCF based temperature sensor using AE and DNN is presented. The proposed model is designed to make appropriate predictions of optical properties even for unknown design space parameters. The comparative metric analysis explores the efficient performance of the model with high values of R-squared ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$r^{2}$ </tex-math></inline-formula> ) score and less computation time in contrast to simulation run-time of FEM. Moreover, the proposed DNN model along with AE is proved to show very low collective mean squared error (MSE) in contrast to DNN without AE.

Plasmon-Enhanced Refractometry Through Cladding Mode Excitation by a Fiber Bragg Grating in Photonic Crystal Fiber

We report on an extrinsic surface plasmon-enhanced refractometer based on cladding mode resonance excitation in a photonic crystal fiber (PCF) equipped with a straight fiber Bragg grating (FBG). First, we show that the lattice pitch and the air hole diameter of the PCF microstructure define the spectral location of the excited cladding mode resonances. Second, we demonstrate that if the PCF parameters are properly selected, those resonances are sensitive to increases in steps of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> refractive index units (RIU) of the refractive index value close to that of water. To the best of our knowledge, this is the first time that the sensitivity of PCF cladding mode resonances to refractive index changes in water-based solutions is reported. We achieved experimental values of 40.3 nm/RIU in terms of wavelength sensitivity and −801 dB/RIU in terms of amplitude sensitivity. The performance of our sensor is therefore comparable to that of tilted FBGs in step-index fibers used for water refractometry, which indicates the potential of our PCF sensor for biosensing. In addition, the sensor fabrication does not require any post-processing such as etching or polishing, which allows preserving the integrity of the fiber probe. Finally, the narrow spectrum within which the PCF operates, allows envisaging multi-target detection with a single fiber probe by using cascaded wavelength-multiplexed gratings.

Design of broadband single-polarization filter based on simple structure photonic crystal fiber with gold-coated air holes

A polarization filter based on simple structure photonic crystal fiber (PCF) coated with gold air holes is designed in this work. The full vector finite element method (FEM) is used to calculate the characteristic parameters of PCF. In the final numerical simulation results, the loss peak in the [Formula: see text] polarization direction is 2305.72 dB/cm and the [Formula: see text]-polarized loss is as low as 75.86 dB/cm at 1.31 [Formula: see text]m. For the fiber length of 1000 [Formula: see text]m, the CT reaches 1936.83 dB and a wide bandwidth greater than 20 dB can provide above 800 nm. The content of this paper can provide a new idea for filter structure design.

An Optimal Design for Decreasing Dispersion in Photonic Crystal Fiber

Fiber optic transmission systems are friendly data transmission systems environmentally due to their low losses, high bandwidth and acceptable reliability. Therefore, they are often used for communication infrastructures. However, the effects of optical loss and dispersion can cause problems in fiber optic communications. In this paper, we mitigate these effects by using photonic crystals. The goal is to minimise the dispersion of the fibers by changing the photonic crystal fiber parameters. Specifically, we change the number, radius, and shape of the holes to minimise dispersion. A new photonic crystal fiber (PCF) is proposed with hexagonal grids of air holes and 11 layers in this structure. An optimal holes number, radius and distance between holes are used to obtain the least dispersion. Next, we use several elliptical and stellar holes to reduce dispersion. The germanium impurity is exploited in the PCF core as a defect. The addition of germanium impurity to the core causes the doping atoms reflect a stronger optical signal with the same attenuated input signal properties. The simulation results show that dispersion value is zero in three points at wavelengths between 1.48 and 1.55 μm. In this wavelength range, the dispersion value was obtained between − 0.3 and 0.6 ps/(nm km).

Design a photonic crystal fiber of guiding terahertz orbital angular momentum beams in optical communication

In this letter, a hollow core ring based circular photonic crystal fiber (PCF) is explored and proposed with stably supporting terahertz (THz) orbital angular momentum (OAM) states transmission. The proposed PCF is discussed, investigated, analyzed and simulated with optical properties in a terahertz frequency spectrum ranging from 0.20 THz to 0.55 THz. The OAM and THz communication-based parameters of the fiber are deliberated extensively under various conditions through using the full vector finite element method (FEM). Some significant parameters of PCF like effective refractive index difference, dispersion profile, confinement loss, effective mode area, numerical aperture, power fraction and isolation effects are numerically discussed for the first time with their effects and applications on the THz OAM transmission. The mentioned PCF has supported 48 OAM modes with a large effective refractive index difference up to 10−3. The confinement loss of the PCF around 10−10 dB/cm, and the average dispersion profile variation is 1.0055 ps/THz/cm. Besides, the highest numerical aperture and power fraction of the PCF are 0.35 and 99.7882%, respectively. Also, a higher isolation power effect around 267 dB, and crosstalk less than −14 dB are obtained for the PCF. Moreover, this kind of PCF would be a robust candidate for efficient THz OAM transmission, high capacity and high feasibility of optical fiber communications.

Methanol-Filled Hybrid Photonic Crystal Fiber with High Birefringent and Negative Dispersion

A unique hexagonal lattice structure of silica-based solid core photonic crystal fiber (PCF) surrounded by array of air holes is proposed. The cladding portion of the structure consists of five rings where core is made up of 11 small rings filled with methanol. Three different-shaped structures are used to analyze the effect on PCF parameters where the first structure uses circular air holes in cladding and core, the second structure consists of circular air holes in cladding and elliptical air holes in core, and the last structure was designed by using elliptical air holes in both cladding and core. Optical properties birefringence, confinement loss, and negative dispersion have been found theoretically and compared. A novel and relatively simple approach depicts the results that attain high birefringence, low confinement loss, and negative dispersion. It is found that the presence of elliptic air holes instead of circular air holes in the core region and the cladding brings higher birefringence, low confinement loss, and highly negative dispersion.

Enhancement of thermal and electro-optical properties of photonic crystal fibers infiltrated with a modified 6CHBT nematic liquid crystal doped with gold nanoparticles

In this paper we present the obtained experimental results for enhancing the parameters of photonic crystal fibers infiltrated with a modified 6CHBT doped with gold nanoparticles. By admixing a special liquid crystalline material we were able to widen the working temperature range of our samples. Doping our liquid crystal mixture with nanoparticles visibly enhances the thermal and electro-optical properties of the infiltrated photonic crystal fibers. Additionally, the use of a specially designed four microelectrode system allowed to decrease voltage. Thanks to the introduced modifications we noticed a significant reduction of threshold voltages (up to 44%), rise times (up to 30%) and fall times (up to 50%).

Design optimization of a highly sensitive spiral photonic crystal fiber for liquid and chemical sensing applications

• Sensitivity coefficient is analyzed for three liquids water, propane and propylene of different refractive indices. • Confinement loss is investigated for the optimized parameters of PCF. • Relative Sensitivity is analyzed for different pitch values. • Sensitivity is investigated for various air filling fraction in the cladding region. In this paper, a spiral shaped photonic crystal fiber (PCF) is proposed for liquid sensing applications. The guiding properties of the proposed PCF are analysed. Sensitivity coefficient is analysed by varying different structural parameters for a wider wavelength range. In addition, confinement loss is also studied at the same wavelengths. The relative sensitivity achieved for the optimized parameters are 56.8%, 58.3% and 62.7% for water (n = 1.33), propane (n = 1.34) and propylene (n = 1.36) respectively. With its low confinement loss and high sensitivity the proposed PCF can be used for liquid and chemical sensing applications.

Ultrasensitive long-period gratings sensor works near dispersion turning point and mode transition region by optimally designing a photonic crystal fiber

A novel and ultrasensitive long-period gratings (LPGs) sensor based on photonic crystal fiber (PCF) has been proposed and theoretically investigated. The surrounding refractive index (SRI) sensitivity can be improved enormously by optimizing structure parameters of PCF to ensure LPGs work near dispersion turning point (DTP). Based on this, mode transition (MT) has been also designed and realized in LPGs based on PCF for the first time to further explore the theoretical limit of sensitivity. The simulation results illustrated that the optimized SRI sensitivity is 67,600 nm/RIU in low RI measurement region (1.334–1.344), which is much higher than that of other reported LPGs sensor based on PCF in previous literatures. The competitive advantages make the proposed sensor has a great application prospect in biosensing field, such as biomolecules detection and label-free immune sensing.

D-shaped photonic crystal fiber plasmonic refractive index sensor based on gold grating.

In this work, we proposed a high-resolution D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor based on gold grating. Gold grating is introduced to modulate the resonance wavelength and enhance the refractive index (RI) sensitivity. Structure parameters of PCF and gold grating are analyzed by the finite element method for optimizing the SPR sensor. The simulation results indicate that air hole pitch, air hole diameter, and gold thickness and grating constant have little influence on the sensitivity of the refractive index, which reduces the requirement of precise processing. For improving the resolution of RI sensing, a two-feature (2F) interrogation method, which combines wavelength interrogation and amplitude interrogation, is used. The maximum theoretical resolution of the SPR sensor reaches to 5.98×10-6 RIU in the range of 1.36-1.38, and the wavelength sensitivity reaches to 3340nm/RIU. The proposed SPR sensor shows potential applications for developing a high-sensitivity, real-time, and fast-response SPR-RI sensor.

Simultaneous measurement of magnetic field and temperature based on photonic crystal fiber with eliminating cross-sensitivity

Measurement of magnetic field is very important in many fields, such as industrial manufacture, marine environmental monitoring, medical testing, etc. However, there is a cross sensitivity between the measurement of magnetic field and the fluctuation temperature in the environment. So how to accurately measure the magnetic field and the temperature simultaneously by eliminating the cross-sensitivity has been an urgent problem. In recent years, photonic crystal fiber (PCF) sensor has been widely used due to its particular advantages, such as high sensitivity, small size and its flexibility of filling various sensitive media into the air hole. So the PCF provides a new idea for designing the high-sensitivity magnetic sensor. In this paper, a new PCF sensing structure based on the mixed effects of directional resonance coupling and surface plasmon resonance (SPR) is proposed. In the cladding of the PCF, one air hole infiltrated with the magnetic fluid (MF) forms a defect core and is used as a directional coupling channel. When the wave vector matching condition is satisfied in the directional coupling channel, the power is transferred from the fiber core region to the clad defect core at a particular wavelength, and a loss peak is generated in the transmission spectrum. The MF has its unique magneto-optical effect. This is because its refractive index changes with external magnetic field. So the loss peak can be shifted with the magnetic field at a fixed temperature. Another air hole coated with a gold nano film and infiltrated with the methylbenzene is used as the SPR channel. So plasmon modes are excited, and the resonance peak occurs when the real part of the effective index of the core mode is equal to that of the SPR mode at a particular wavelength. The resonance peak can also be shifted with the index of the methylbenzene at changed temperature. The simulation and numerical analysis of the magnetic field and temperature sensing characteristics of the structure are carried out, and the structure parameters of PCF are optimized by COMSOL Multiphysics through using the finite element method under the boundary condition of perfectly matched layer. In a magnetic field range of 90-270 Oe and in a temperature range of 25-60 ℃, the highest magnetic field sensitivity and temperature sensitivity are respectively 1.16 nm/Oe and -9.07 nm/℃, each with a good linearity in the sensing structure. To eliminate the cross sensitivity between the temperature and magnetic field, a sensitivity coefficient matrix is established. As a result, the highly sensitive double-parameter detection of magnetic field and temperature is realized. Moreover, this sensing structure can be used in an extensive range, which has a certain potential value and practical significance.

Investigation of temperature sensing characteristics in selectively infiltrated photonic crystal fiber.

In this paper, we investigate and experimentally demonstrate the influences of distance between the silica core and the glycerin core of a selectively glycerin-infiltrated photonic crystal fiber (PCF) on the mode characteristics, as well as the temperature sensitivity. By comparing the simulation and experiment results of three single-void glycerin-infiltrated PCFs with the glycerin core being one period, two periods and three periods away from the silica core respectively, it reveals that the smaller distance between the silica core and the glycerin core does not affect the modes indices, but increases the intensities of modes in the glycerin core and thus enhances the temperature sensitivity. Consequently, the temperature sensitivity can be controlled and tuned by appropriately designing the structure parameters of glycerin-infiltrated PCF. Besides, the highest temperature sensitivity up to -3.06nm/°C is obtained in the experiment as the glycerin core is nearest to the silica core. This work provides insights into the design and optimization of the liquid-infiltrated PCF for sensing applications.

Simplified Loss Estimation of Splice to Photonic Crystal Fiber using New Model

AbstractFor a range of fiber parameters and wavelengths, the splice losses between photonic crystal fiber and a single mode fiber are calculated using our simplified and effective model of photonic crystal fiber following a recently developed elaborate method. Again, since the transverse offset and angular mismatch are the serious factors which contribute crucially to splice losses between two optical fibers, these losses between the same couple of fibers are also studied, using our formulation. The concerned results are seen to match fairly excellently with rigorous ones and consistently in comparison with earlier empirical results. Moreover, our formulation can be developed from theoretical framework over entire optogeometrical parameters of photonic crystal fiber within single mode region instead of using deeply involved full vectorial methods. This user-friendly simple approach of computing splice loss should find wide use by experimentalists and system users.

Simulation analysis of a temperature sensor based on photonic crystal fiber filled with different shapes of nanowires

We propose a photonic crystal fiber (PCF)-based surface plasmons resonance (SPR) temperature sensor in this paper, and using the dual function of PCF filled with different shapes of nanowires and analyte to realize temperature sensing and have designed an experimental setup. Different shapes of nanowires with the mixed liquid are filled into the proposed octagon PCF. The simulation results indicate that not only structure parameters of PCF but also the shapes of filled nanowires play a key role to the sensing. A blue-shift in the SPR resonant peak is shown with the temperature increases. Different loss spectra present that a higher confinement loss for low temperature and the octagon PCF filled with elliptical nanowires shows a more obvious peak shift and higher sensitivity, which is about 500pm/°C and the corresponding sensor resolution is 2.0×10−2°C. This PCF sensing system has great practical value and significance for its advantage of high sensitivity.