Photonic Crystal Fiber Structure Research Articles

Flattened zero dispersion Photonic crystal fibers with embedded nano holes and ultra low confinement loss for supercontinuum generation

In this paper unique photonic crystal fiber (PCF) structure with nanoholes embedded have been studied. Embedded nanoholes have been filled with different materials of alcoholic groups like butanol, ethanol, methanol and propanol. Investigations of these structure shows flattened zero dispersion in visible range to far infrared regions. Simulated PCF structure reports ultra-low confinement loss of the order of 10-8 dB/km. Designed PCF promises to give large nonlinear coefficient of 3000 W-1Km-1 at 1335nm wavelengths. Numerical simulation of the fiber for the generation of supercontinuum generation (SCG) has been performed. Low power pump pulses of 50fs duration have been used. With a fiber of length of 15cm and pulses of 1kW, 2kW, 5kW and 10kW peak power, supercontinuum broadening of about 607nm, 908nm, 1987nm and 2405nm respectively.

High birefringent, low loss and flattened dispersion asymmetric slotted core-based photonic crystal fiber in THz regime

This paper proposes a novel model to attain high birefringence and low loss in a slotted core-based photonic crystal fiber (PCF) structure in THz regime. The performance of the proposed PCF has been evaluated by applying finite element method (FEM) with full simulation software COMSOL Multiphysics V-5.1. The proposed model gains good optical properties such as high birefringence of 0.24, low effective material loss (EML) of 0.03 cm[Formula: see text], low confinement loss of 6.5 × 10[Formula: see text] (dB/m), low scattering loss of 2 × 10[Formula: see text] (dB/m) and low bending loss of 7.4 × 10[Formula: see text] (dB/cm). The proposed structure also exhibits the flattened dispersion for wider frequency response. However, the real-life fabrication of the suggested model is highly feasible using the current technology due to the unique shape of circular air holes in the cladding region. The outcomes make the proposed PCF a stronger candidate for polarization-preserving applications such as sensing, communications and filtering operations in THz band.

Terahertz detection of toxic gas using a photonic crystal fiber

Abstract The photon energies of molecules falling rightly into the terahertz region offers a high potential for gas detection. However, detecting gas at low concentration is difficult because of the weak dipole moments of gas in the terahertz region. Here, a unique structure of porous core photonic crystal fiber (PCF) sensor with a high sensitivity for gas detection is proposed. The dependences of the mode field distribution and the propagation loss of PCF sensor on the porosity are studied to optimize for a higher sensitivity. For the optimal PCF with a porosity of 50%, the mode field is strongly confined in the air holes in the core, and the propagation loss can reach as low as 0.013 dB/m. The detection of a toxic gas (hydrogen cyanide) is also investigated to demonstrate the sensing performance of the proposed PCF. A low concentration of 2 ppm under the standard atmosphere pressure (1 atm) can be detected based on the resonance frequency of the hydrogen cyanide. The length of the proposed PCF is just 100 mm, which is much shorter than the traditional optical fiber with several meters long. Our results provide a novel approach for the detection of toxic gas in air pollution monitoring using terahertz spectroscopy.

Numerical Investigation of Supercontinuum Generation Through AsSe2/As2S5 Chalcogenide Photonic Crystal Fibres and Rib Structures

We compare numerically the supercontinuum generation (SCG) phenomenon in the Mid-Infrared (MIR) region through AsSe2/As2S5 chalcogenide based optical waveguides namely photonic crystal fiber (PCF) and rib-like structures. The same material combination is used in the two configurations for MIRSCG. Specifically, the studied PCF is composed of a core made of AsSe2 glass and a surrounding cladding made of As2S5 glass while the AsSe2/As2S5 chalcogenide rib waveguide (AsSe2/As2S5-ChRW) is filled in its upper cladding by air while the lower one is constituted by the As2S5 glass. The comparison is conducted in the anomalous dispersion regime on a very short 1 mm-length of propagation for a 50 fs sechtype pulse in the HE11 mode at 4 μm wavelength for each waveguide. Despite the ultra-broadband and coherent MIR-SCG spectrum of 18.75 μm in bandwidth obtained with the considered AsSe2/As2S5-PCF, we found that an AsSe2/As2S5-ChRW that has a height H = 1.98 μm and a width W = 5 μm allows a SCG spanning approximately from 1 beyond 20 μm with a very low energy as 0.4 nJ.

Refractive index sensor based on high-order surface plasmon resonance in gold nanofilm coated photonic crystal fiber**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFC0110301), the National Natural Science Foundation of China (Grant Nos. 61575219, 91850209, and 11434016), the College Young Talents Program of Hebei Province, China (Grant No. BJ2018040), the Hebei University of Science

We propose a novel kind of wide-range refractive index optical sensor based on photonic crystal fiber (PCF) covered with nano-ring gold film. The refractive index sensing performance of the PCF sensor is analyzed and simulated by the finite element method (FEM). The refractive index liquid is infiltrated into the cladding air hole of the PCF. By comparing the sensing performance of two kinds of photonic crystal fiber structures, a wide range and high sensitivity structure is optimized. The surface plasmon resonance (SPR) excitation material is chose as gold, and large gold nanorings are embedded around the first cladding air hole of the PCF. The higher order surface plasmon modes are generated in this designed optical fiber structure. The resonance coupling between the fundamental mode and the 5th order surface plasmon polariton (SPP) modes is excited when the phase matching condition is matched. Therefore, the 3rd loss peaks appear obvious red-shift with the increase of the analyte refractive index, which shows a remarkable polynomial fitting law. The fitnesses of two structures are 0.99 and 0.98, respectively. When the range of refractive indices is from 1.40 to 1.43, the two kinds of sensors have high linear sensitivities of 1604 nm/RIU and 3978 nm/RIU, respectively.

Chirped Large Mode Area Photonic Crystal Modal Fibers and its Resonance Modes Based on Finite Element Technique

Abstract The study has outlined the finite element technique used for the fiber modal analysis of photonic crystal fiber (PCF) structure with a hexagonal/circular air holes arrangement on the cladding of pure fiber-optic silica. The used fibers that are namely highly nonlinear fiber (HNLF), single model silica fiber (SMSF) are combined with PCFs with different dopants concentration. Leakage loss, number of guided resonant modes, fiber birefringence, effective refractive index and cross-section areas and nonlinear coefficient parameters are measured inaccurate estimation. The optimum resonant guided modes are also estimated for different lattice infrastructure in circular PCFs.

Elliptical-hole PCF structure with selective Y-axis gold coating for tunable single-polarization band-stop filtering

An elliptical-hole photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is proposed, which can work as a tunable single-polarization band-stop filter (BSF). Theoretical results show that the proposed structure is very sensitive to the polarization of the guided modes, due to its high birefringence coefficient and strong SPR effect. It can achieve single-polarization single-mode (SPSM) filtering without liquid filled in the gold coated air holes. At resonant wavelength, the loss of the y polarization fundamental mode reaches 792.16 dB cm−1, but the loss of the x polarization fundamental mode is only 0.52 dB cm−1, causing that the extinction ratio is as high as 688 dB and the bandwidth is larger than 520 nm with the PCF length of 1 mm. When liquids with the refractive index (RI) ranging from 1.44 to 1.48 are filled in the gold coated air holes, the PCF could be used as a BSF to filter the x polarization fundamental mode selectively on the premise of SPSM filtering. And the center wavelength of the BSF is extremely sensitive to the liquid RI with a high sensitivity of 16 820 nm/RIU, which indicates a potential application in RI sensing. The proposed PCF realizing the integration of SPSM filter and BSF is available for compact optical communication systems.

A Novel Polarization Filter Based on Photonic Crystal Fiber with a Single Au-Coated Air Hole and Semi-Hourglass Structure

A polarization filter that has a novel photonic crystal fiber structure of semi-hourglass part and Au-coated film is proposed. We simulated the performance of the structure by the finite element method. The numerical simulation results show that altering the structure parameters and the thickness of Au film can lead to an optimal parameter combination with remarkable features, owing to the semi-hourglass part that induced huge asymmetry factor into the structure. On the one hand, when the thickness of Au film is controlled to be 18.7 nm, we can get the confinement loss 1304.02 dB/cm and 3.96 dB/cm on y-polarization and x-polarization respectively at λ = 1.55 μm. On the other hand, controlling the thickness to 35 nm, the confinement loss on y-polarization and x-polarization is 848.87 dB/cm and 1.31 dB/cm respectively at λ = 1.31 μm. In addition, the bandwidth with crosstalk smaller than − 20 dB is 680 nm and 800 nm at λ = 1.55 μm and 1.31 μm, respectively, when the fiber length is 500 μm. This structure, as a reference, can provide a new idea when designing a photonic crystal fiber structure applied in optical communication and sensor system.

Surface-enhanced Raman scattering-active photonic crystal fiber probe: Towards next generation liquid biopsy sensor with ultra high sensitivity.

The tremendous enhancement factors that surface-enhanced Raman scattering (SERS) possesses coupled with the flexibility of photonic crystal fibers (PCFs) pave the way to a new generation of ultrasensitive biosensors. Thanks to the unique structure of PCFs, which allows direct incorporation of an analyte into the axially aligned air channels, interaction between the analyte and excitation light could be increased many folds leading to flexible, reliable and sensitive probes that can be used in preclinical or clinical biosensing. SERS-active PCF probes provide unique opportunity to develop an opto-fluidic liquid biopsy needle sensor that enables one-step integrated sample collection and testing for disease diagnosis. Specificity being a key parameter to biosensors, the PCF inside the biopsy needle could be functionalized with targeting moieties to detect specific biomarkers. In this review article, we present some of the most promising recent biosensors based on PCFs including hollow-core PCFs, suspended-core PCFs and side-channel PCFs. We provide a wide range of applications of such platform using Raman spectroscopy, label free SERS or labeled SERS detection and analyze some of the main challenges to be addressed for translating it to a clinically viable next generation sensitive biopsy needle sensing probe.

Effect of Ge Nanoparticles in the Core of Photonic Crystal Fiber on Supercontinuum Generation

The effect of Ge nanoparticle (Ge NP) incorporation in the germanosilicate glass core of the photonic crystal fiber (PCF) on supercontinuum generation (SCG) was investigated. The Ge NP-doped germanosilicate glass core PCF was fabricated by using the modified chemical vapor deposition (MCVD) and the stack-and-draw processes. The average diameter of Ge NPs embedded in the core of the PCF was 4.2 nm. The absorption peaks at 480 nm and 515 nm and the band from 600 to 800 nm were attributed to the Ge NPs in the core of the PCF. SCG of the 490 nm bandwidth (598 nm~1088 nm) with a conversion efficiency of 31% was obtained by pumping at 800 nm with the Ti:sapphire femtosecond laser of 160 mW with 35 fs pulse at 1 kHz repetition rate, resulting from the enhanced optical nonlinearity from Ge NPs as well as the PCF structure of the fiber.

Surface plasmon resonance sensor based on symmetrical side-polished dual-core photonic crystal fiber

• Symmetrical polishing structure of dual-core photonic crystal fiber. • Gold layer is plated on the symmetrical side-polished surface of PCF to excite the surface plasmon polaritons. • The proposed sensor is able to detect the analyte the refractive indexes in the range of 1.3–1.42. • The maximum sensitivity of the proposed sensor is 8000 nm/RIU. A surface plasmon resonance (SPR) sensor based on symmetrical side-polished dual-core photonic crystal fiber (DC-PCF) with a wide refractive index (RI) detection is proposed and analyzed. A gold layer is placed on the symmetrical side-polished surface of photonic crystal fiber to excite the surface plasmon polaritons (SPPs). The proposed DC-PCF consists of the symmetrical air-holes and symmetrical side-polished structure. The design without air holes on both sides of the core can efficiently realize phase matching between the core guided mode and the plasma mode. Numerical simulation results show a maximum sensitivity as high as 8000 nm/RIU (refractive index unit) with a resolution of 1.3 × 10 −5 RIU. It has a significant advantage in the field of chemical and biological detection because it is able to detect the analyte RI in the range of 1.3–1.42.

Numerical evaluation of the performance of different materials in nonlinear optical applications

Abstract In this research paper, a D-shape structure of photonic crystal fiber (PCF) is introduced. Here, prime optical transmission characteristics like as nonlinearity, numerical aperture (NA), effective area, confinement loss are obtained by selecting finer mesh and finite element method (FEM). Gallium phosphide (GaP), Tellurite, Silicon Nano Crystal, and Chalcogenide are separately used as a core material and they show better performance than previously published articles. Silicon nanocrystal provides the nonlinearity of 52358618.29 W−1Km−1, GaP of 3471273.165 W−1Km−1, chalcogenide of 3584986.3 W−1Km−1 and tellurite of 307870.6261 W−1Km−1 at the operating wavelength 0.1 μm. With our best of knowledge, the performance of different ceramics materials in optical nonlinear applications is evaluated for the first time. This structure also lends little mode area of 1.20 × 10−13 m2, low confinement loss of 4.32 × 10−4 at the wavelength 0.1 μm and high numerical aperture of 0.86 at 1.5 μm. All these outcomes can play an important role in biomedical imaging, sensing, supercontinuum application, amplification of optical parameter, and other nonlinear applications.

Designing the Structure of Photonic Crystal Fibers for the Generation of Broadband Single Photon States

Structures of photonic crystal fibers are proposed for the generation of broadband single photon states using the process of spontaneous four-wave mixing. New types of structures are modeled mathematically. The spectral and correlation characteristics of the generated states are calculated.

Highly birefringent do-octagonal photonic crystal fibers with ultra flattened zero dispersion for supercontinuum generation

Abstract Photonic crystal fiber (PCF) structures with do-octagonal geometry have been studied. These do-octagonal PCF structure have smaller circular holes arranged in rhombic fashion at its centre. Moreover, these small holes are doped with materials like butanol, ethanol, methanol and propanol. Do-octagonal PCF structures doped with methanol and air filled structure report very high birefringence. Ultra flattened zero dispersion has been achieved by all the simulated structures. Besides, low confinement loss and large nonlinearity have also been reported. Numerical simulation for supercontinuum generation has been performed. Supercontinuum spectra obtained for peak power 1 kW, 2 kW, 5 kW and 10 kW are 650 nm, 950 nm, 1450 nm and 2050 nm respectively.

Design and Analysis of Surface-Plasmon-Resonance-Based Photonic Quasi-Crystal Fiber Biosensor for High-Refractive-Index Liquid Analytes

We propose a sixfold photonic quasi-crystal fiber with a trapezoidal analyte channel based on surface plasmon resonance for the detection of high-refractive-index (RI) liquid analytes and numerically analyze its sensing performance for different liquid analyte refractive indices and heights using the finite-element method. In contrast to the common D-shaped structure photonic crystal fiber, we design a trapezoidal analyte channel to investigate the role of the sample liquid height within the channel and discussed the feasibility of the fabrication process. We find that with various liquid analyte heights ratios of 20%, 25%, 30%, and 50% of the maximum channel height, the proposed biosensor exhibits linear sensing performance with a maximum RI sensitivity of 4400, 6100, 8000, and 17000 nm/RIU, respectively, for analytes RI range of 1.44–1.57, 1.41–1.51, 1.40–1.49, and 1.40–1.44. This sensor is suitable to detect various high RI chemicals, biochemicals, and organic chemical samples. Owing to its simple structure of the proposed biosensor with promising linear sensing performance, we envisage that this biosensor could turn out to be a versatile and competitive instrument for the detection of high-RI liquid analytes.

Propagation Controlled Photonic Crystal Fiber-Based Plasmonic Sensor <italic>via</italic> Scaled-Down Approach

Light trapping capability is the key phenomena of the photonic crystal fiber (PCF) which paves the broad range of applications. In this work, we control the light-guiding direction of the proposed PCFs via scaled-down approach to enhance the coupling between core-guided mode and surface plasmon polariton (SPP) mode resulting in the increase of sensitivity. We introduce the scaled-down air-holes in the first and second rings of the proposed PCF which provides the light guiding capability through the desire scaled-down region. A chemically stable plasmonic material gold is used outside the PCF structure to facilitate the detection of unknown analyte externally. Finite element method is used for numerical investigations, and the sensor performance is investigated by following the wavelength and amplitude interrogation methods. The proposed sensor shows the maximum wavelength sensitivities of 30000 and 22000 nm/RIU, and the maximum amplitude sensitivities of 1212 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 1506 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for x- and y-polarized modes, respectively in the analyte refractive index (RI) range of 1.33 to 1.39. It also shows high sensor wavelength resolution of 3.33 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> RIU and 4.54 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> RIU, and a figure of merit about 508 and 500 for x- and y-polarized modes, respectively. It should be noted that the proposed PCF SPR sensor shows the significant sensing response for both polarization modes, as a result it will provide more freedom in choosing light source during practical implementation. Furthermore, the finding results indicates the proposed sensor will be effective for the detection of organic chemicals, biomolecules and medical diagnostics.

Degenerate four-wave mixing for measurement of magnetic field using a nanoparticles-doped highly nonlinear photonic crystal fiber.

A novel magnetic field sensor based on the degenerate four-wave mixing (DFWM) technique is theoretically proposed using a As2S3-core silica-cladding photonic crystal fiber (PCF). In order to enhance the sensitivity, we put forth a novel design of highly nonlinear PCF where the silica cladding is doped with either Au, Ag, or Al metallic nanoparticles. The effect of volume fraction of the nanoparticles within the cladding and the size of nanoparticles are considered as the control parameters in designing the magnetic field PCF sensor to obtain high sensitivity using this novel DFWM scheme. The PCF structure of the proposed sensor is optimized with the proposed pitch of 3μm and air hole diameter of 2.78μm. We consider a pumping pulsed laser light with a wavelength of 2100nm in the mid-IR regime. It has been found that the optimized PCF with Al-SiO2-cladding with small volume fraction and small nanoparticle size possess magnetic field sensitivity values of 2.74 and -0.058 nm/Oe for the Stokes and anti-Stokes gain lines.

Modified Structure Of Photonic Crystal Fiber With Dispersion And Confinement Loss Properties For Wideband Applications

In this article, an optimized structure of Photonic Crystal Fiber (PCF) has been planned that investigates the effect of dispersion and confinement loss of square shaped photonic crystal fiber, intended for wideband applications ranges from 1.35um to 1.70um. The objective of the suggested geometry is to attain such optical properties by fluctuating its parameters like pitch, number of outer circular rings and inner elliptical rings to make it flexible and simple for manufacturing. Finite Element Method and Perfectly Matched Boundary layer (PML) is set for this proposed geometry. Moreover, recommended PCF structure has unlimited application value in the fiber-optic communications such as fiber lasers, highly sensitive gas sensors, nonlinear devices, high-power transmission and much more.

Review on Photonic Crystal Fibers With Hybrid Guiding Mechanisms

Photonic crystal fibers (PCFs) with hybrid guiding mechanisms have undergone substantial development in recent years. Due to the co-existence of index-guiding and photonic bandgap (PBG)-guiding mechanisms in this special class of PCFs, many peculiar properties have been investigated and demonstrated as advantageous and favorable in many applications. This review paper provides a comprehensive review of the recent progress of these hybrid guiding PCFs. The first part explains the principles of the hybrid guiding mechanisms in the PCF structures. The hybrid guiding PCFs are realized in three approaches, including polarization-dependent hybrid guiding PCFs, radial hybrid guiding PCFs, and two-core hybrid guiding PCFs. This is followed by a review of various development and applications for each type of hybrid guiding PCFs in the second part, including tunable filters, high power lasers, nonlinear optics, and polarization optics and sensing applications. Finally, the considerations and challenges on the potential applications of the hybrid guiding PCFs are discussed.

Simultaneous measurement of temperature and strain based on dual SPR effect in PCF

A novel Photonic Crystal Fiber (PCF) structure with dual Surface Plasmon Resonance (SPR) was proposed to implement simultaneous measurement of temperature and strain and resolve the cross-sensitivity problem between temperature and strain. Two symmetrical holes of the PCF was coated with golden layer and one of which was infiltrated with temperature-sensitive liquid. Through theory and numerical analyses, the influences of temperature and strain on structural parameters of the PCF were discussed and calculated. Simulation results demonstrated that the temperature and strain could be simultaneously measured with sensitivities of −6.83 nm/°C and 1.30 × 10−3 nm/με, respectively, when diethylene glycol was chosen as the temperature sensitive liquid. In particular, the influence of strain variation on the temperature sensing characters was analyzed and compensated, which could further guarantee the measurement precision of temperature.