Solid-core Photonic Crystal Fiber Research Articles

Chalcogenide Ge20Sb5Se75 photonic crystal fiber with seven air-hole rings for ultraflat mid-infrared supercontinuum generation

Supercontinuum (SC) generation in solid-core circular photonic crystal fibers (PCFs) made of Ge20Sb5Se75 is numerically analyzed. A large core is projected to increase light coupling efficiency into selected PCFs as well as raise coupling to standard silica fibers. High nonlinear coefficient and near-zero flat dispersion allow ultraflat SC spanning 1.5–4.6 μm in an all-normal dispersion regime. This requires 3 kW of peak power with 180 fs of pulse duration. The fiber with one zero-dispersion wavelength (ZDW) generates SC bandwidth in the range of 1.54–7.39 μm at 3.5 μm using peak power of 10 kW. For the same input power, the SC spectral covers from 1.39 to 7.36 μm in 10 cm of fiber with two ZDWs. These are wider SC bandwidths than those of previous chalcogenide fibers reached with lower peak powers. Therefore, the proposed Ge20Sb5Se75 PCFs are excellent candidates for the broadband ultraflat mid-infrared SC spectra used in high-speed nonlinear imaging and frequency measurement.

Innovative suspended ring core fiber for SERS application

Solid core photonic crystal fibers (SC-PCFs) have garnered attention as probes for surface-enhanced Raman spectroscopy (SERS) due to their potential as optofluidic devices, offering heightened sensitivity and reliability compared to traditional planar/colloidal nanoparticle-based SERS platforms. A smaller core allows for more light interaction but might compromise sensitivity and reliability due to reduced surface area for interaction. Here, we introduce an innovative SC-PCF design aimed at resolving the trade-off between increasing the evanescent field fraction and the core surface area. By substituting a suspended silica rod with a suspended thin-silica ring, we augment the surface area for attached nanoparticles by one order of magnitude while retaining a substantial amount of evanescent light interaction with the analyte. Experimental findings showcase an improved sensitivity in SERS signal compared to previously reported top-performing PCF sensor designs. Importantly, with necessary refinement and optimization, this innovative fiber design extends beyond SERS applications, potentially amplifying the sensitivity of various other fiber-based sensing platforms.

Mechanically induced long period gratings in different silica multi-layered optical fibers

This work presents a thorough comparative investigation of mechanically induced long period gratings (MILPGs) realized in different unconventional multi-layered silica optical fibers: two double cladding fibers (DCF), with progressively three layered (PTL) and W-type structures, and a solid core photonic crystal fiber (PCF). A periodic interdigitated grooved structure, based on the stereo-lithography 3D printing technique, is developed for the grating formation in these fibers with simplicity and cost-effectiveness. Multiple grating periods are developed in the range 480–660 μm, resulting in attenuation bands with depth within 15–25 dB and wide range of tunability over the wavelength range of 1100–1700 nm. The results demonstrate effective management of transmission spectra evolution as a function of the applied weight, with minimal alteration in wavelength position when testing the fiber with or without its coating. Polarization dependent properties of these gratings are also investigated demonstrating a negligible impact. This is the first time that such a broad investigation is conducted about MILPGs in the fibers mentioned earlier with broad scouting in fabrication parameters, opening to the application of such devices for sensing and communication purposes.

Solid-core photonic crystal fiber with high acoustic pressure sensitivity

This study reports the design and fabrication of a Φ60/100-μm solid-core photonic crystal fiber with high acoustic pressure sensitivity. By decreasing the diameter of the cladding and increasing the proportion of air holes in the cladding, the equivalent Young’s modulus of the cladding was reduced, and the acoustic pressure sensitivity of the optical fiber was improved. The simulation and test results showed that the acoustic pressure sensitivity of the fabricated Φ60/100-μm solid-core photonic crystal fiber is approximately five times higher than that of the conventional Φ125/250-μm single-mode fiber.

Research on application of secondary drawing technology in the preparation of various solid-core and hollow-core photonic crystal fibers

This paper presents a method of fabricating photonic crystal fiber by secondary drawing technology combined with air pressure regulation. The internal structure of optical fiber is solidified and shaped by primary drawing. The core diameter of PCF is reduced to less than 4μm by adding glass sleeve in secondary drawing. Multi-core PCF is prepared, and the curvature and temperature of two-core PCF are measured. Fan-shaped PCF, band gap PCF, silver-filled PCF and V-shaped PCF are prepared, and the dispersion and loss of V-shaped PCF are simulated. The drawing parameters are fitted and compared. The parameter curve of furnace temperature presents an upward concave shape, and the parameter curve of air pressure threshold presents an upward convex shape. These fitting curves have reference value for the preparation of PCF in the future.

Axi-Stack: a method for manufacturing freeform air-silica optical fibre.

We present a method with potential for fabricating freeform air-silica optical fibre preforms which is free from the stacking constraints associated with conventional stack-and-draw. The method, termed Axi-Stack, is enabled by the precision machining of short cross-sectional preform discs by ultrafast laser assisted etching; a laser-based microfabrication technique which facilitates near arbitrary shaping of the preform structure. Several preform discs are stacked axially and fused together via ultrafast laser welding to construct the preform, which can be drawn to fibre using conventional methods. To illustrate the Axi-Stack process, we detail the fabrication of a 30 cm long solid-core photonic crystal fibre preform with a square lattice of cladding holes and characterise fibre drawn from it.

Experimental studies on the core-structure dependence of backward Brillouin gain in solid-core photonic crystal fibers.

Stimulated Brillouin scattering (SBS) in solid-core photonic crystal fibers (PCFs) differs significantly from that in standard optical fibers due to the tight confinement of both optical and acoustic fields in their µm-sized fiber cores, as resultantly evident in their Brillouin gain spectra. Despite many theoretical studies based on either simplified models or numerical simulations, the structural dependency of Brillouin gain spectra in small-core PCFs has not been characterized comprehensively using PCFs with elaborated parameter controls. In this work we report a comprehensive characterization on the core-structure dependences of backward SBS effects in solid-core PCFs that are drawn with systematically varied core-diameter, revealing several key trends of the fiber Brillouin spectrum in terms of its gain magnitude, Brillouin shift and multi-peak structure, which have not been reported in detail previously. Our work provides some practical guidance on PCF design for potential applications like Brillouin fiber lasers and Brillouin fiber sensing.

Numerical Analysis of Solid-Core Photonic Crystal Fiber Based on Plasmonic Materials for Analyte Refractive Index Sensing

In this study, we presented a simple highly sensitive sensor based on commercially available solid-core photonic crystal fiber (PCF) and surface plasmon resonance (SPR) for measuring the refractive index (RI) of analytes. The numerical simulation based on the finite element method (FEM) has been examined to compute the optical properties such as confinement loss, power spectrum, and transmission intensity of the sensor. The most sensitive and inert plasmonic materials (gold and silver) have been assumed to be coated inside the fiber with the range of analyte RI from 1.32 to 1.40. The performance of the proposed sensor has been evaluated by tracing the several optical features like wavelength sensitivity, amplitude sensitivity, resolution of the sensor, and figure of merit. As a result, the comparative study between silver and gold elements has been carried out in which the maximum sensitivity received was 1.15 μm/RIU and 1.10 μm/RIU, respectively. Whereas, on the base of power spectrum, the obtained sensitivity was 513 μm/RIU for the gold layer. Moreover, the effect of other structural parameters (air holes and plasmonic layer thickness) on the sensing performance has been taken into an account. According to the simulation analysis and results, this sensor would have a great potential in various sensing applications of biomedical and liquid refractive index.

Enhancement of blue and ultraviolet components in PCF-based supercontinuum generation through inter-modal dispersive-wave radiation.

Broadband supercontinuum (SC) light sources generated through nonlinear effects in solid-core photonic crystal fibers (PCFs) have been widely used in spectroscopy, metrology, and microscopy, leading to great application successes. The short-wavelength extension of such SC sources, a longstanding challenge, has been the subject of intensive study over the past two decades. However, the exact mechanism of blue and ultraviolet light generation, especially for some resonance spectral peaks in the short-wavelength regime, is not yet fully understood. Here, we demonstrate that the effect of inter-modal dispersive-wave radiation, which results from phase matching between pump pulses at the fundamental optical mode and packets of linear waves at some higher-order modes (HOMs) propagating in the PCF core, might be one of the critical mechanisms that can result in some resonance spectral components with wavelengths much shorter than that of the pump light. We observed in an experiment that several spectral peaks resided in the blue and ultraviolet regimes of the SC spectrum, whose central wavelengths can be tuned by varying the PCF-core diameter. These experimental results can be interpreted well using the inter-modal phase-matching theory, providing some useful insights into the SC generation process.

Design and analysis of low loss solid-core hexagonal photonic crystal fiber for applications in terahertz regime

An index-guiding novel solid-core photonic crystal fiber (SC-PCF) formed by a hexagonal lattice of circular-shaped air holes arranged in silicon background is realized. By varying the radius ‘r’ of the air holes from 0.1a to 0.5a (where ‘a’ is defined as the lattice constant), the characteristic electromagnetic modes of the low loss Terahertz (THz) fiber were solved through eigenmode analysis using finite element method (FEM). The effective mode area and the nonlinearity of the proposed PCF are calculated for different radii of the air holes and it is found that the effective mode area decreases when the radius of the air holes is increased. On the other hand, the nonlinearity increases for an increase in the air holes radii. At 1 THz, the confinement loss of the proposed fiber is in the order of 10−23 dB/m and transmittance efficiency above 96% has been attained. As 5-G technology emanates, THz wave propagation becomes essential and the designed hexagonal lattice SC-PCF will be useful for the advancement of communication systems, sensing devices and several medical applications.

Terahertz Wave Propagation Characteristics in Graded Teflon Based Solid-Core Photonic Crystal Fibre

In the past few years, photonic crystal fibre (PCF) in the Terahertz spectrum is drawing significant attention because of its multifaceted applications in high-speed data communication, spectroscopy, sensing, etc. The proposed PCF structure is based on a Teflon solid core surrounded by porous cladding. Teflon has been used as a background material because of its high flexibility and the possibility of making longer PCFs, which is capable of guiding waves in the THz region. The porous cladding consists of circular air-holes positioned hexagonally whose diameters increase with each subsequent layer keeping the pitch constant thus providing a graded-index profile. The diameters of air holes in each hexagonal layer are 1 mm, 1.2 mm and 1.5 mm respectively, maintaining a constant pitch of 2mm and a perfectly matched layer (PML) thickness of 3mm. We have examined the transmission characteristics of the proposed profile in the frequency range of 0.8 THz to 2.5 THz. The modal solution of the profile is solved using the Finite Element Method based on COMSOL Multiphysics version 5.5. Using the graded-index profile, we have obtained a large effective modal area of around 5.6 mm2 at 1 THz and a low confinement loss of 2.25 × 10−4 dB/km at the same frequency. Due to this large effective modal area, we get higher damage threshold and weaker non-linear effects, making it suitable for high power applications.

Nonlinear properties of circular solid-core photonic crystal fiber with air-hole diameter difference and spacing in the cladding

We emphasize the ability to control the nonlinear properties of silica-based circular solid-core photonic crystal fibers (PCFs) with a new design. In this fiber, the diameter of the air hole in the rings is different, and the lattice constant is ununiform in the cladding. The simulation results show that a near-zero ultra-flattened chromatic dispersion over a wide wavelength range and low attenuation in these PCFs is achieved. Two structures with the lattice constant, Ʌ, of 0.7 and 0.9 µm and filling factor, d1/Ʌ, of 0.45 in the first ring were selected and investigated in detail. These structures are capable of generating broad-spectrum supercontinuum.

Study on dispersion characteristics of square solid-core photonic crystal fibers with As2S3 substrate

The dispersion characteristics of As2S3 solid-core photonic crystal fibers were investigated with the change of structural parameters including filling factor ( ) and lattice constant ( ). Photonic crystal fiber obtained diverse dispersion including all-normal and anomalous dispersion with two zero-wavelengths dispersion at all values of lattice constant investigated. The dispersion value increases when the lattice constant increases and the filling factor decreases. Photonic crystal fiber has a flat dispersion curve and closeness to the zero-dispersion curve in the long-wavelength range are advantages of this design. Based on the analysis of numerical simulation results, we have proposed two structures with optimal dispersion for the application of supercontinuum generation.

Optimization of optical properties of Ge20Sb5Se75-based photonic crystal fibers

In this paper, we present a new design of solid-core photonic crystal fiber (PCF), a Ge20Sb5Se75 substrate with a hexagonal lattice structure. The fiber characteristics are studied in the long-wavelength range (from 1.5 µm to 7.0 µm). A full modal analysis and optical properties of designed photonic crystal fibers with lattice constant Λ and filling factor d/Λ are presented in terms of chromatic dispersion, effective refractive index, nonlinear coefficients, and confinement loss. All-normal and anomalous flat dispersion with high nonlinearity and low confinement loss are the outstanding advantages of these photonic crystalline fibers. From there, three optimal structures with Ʌ = 2.0 µm, d/Ʌ = 0.35; Ʌ = 2.5 µm, d/Ʌ = 0.3 and Ʌ = 3.0 µm, d/Ʌ = 0.3 are selected and analyzed in detail for application in supercontinuum (SC) generation.

NONLINEAR CHARACTERISTICS OF SQUARE SOLID-CORE PHOTONIC CRYSTAL FIBERS WITH VARIOUS LATTICE PARAMETERS IN THE CLADDING

Nonlinear characteristics of fused silica, solid-core photonic crystal fibers (PCFs) with a square array of air holes are studied numerically. We present a novel design that emphasizes the difference in air hole diameters in the photonic cladding. These PCFs have the advantages of flat dispersion, high nonlinearity, and low attenuation. Based on simulation results, three optimal structures, denoted #F1, #F2, and #F3, having anomalous and all-normal dispersions in the near-infrared range are selected to investigate characteristic properties at the pump wavelength. Such PCFs open up many possibilities for nonlinear optical applications, especially supercontinuum generation.

INFLUENCE OF STRUCTURAL PARAMETERS ON OPTICAL CHARACTERISTICS OF PHOTONIC CRYSTAL FIBERS WITH CIRCULAR LATTICE

We demonstrate in this study that near-zero, ultra-flattened chromatic dispersion can be achieved over a wide range of wavelengths in photonic crystal fibers (PCFs) by means of slight variations in the geometrical parameters of the cladding. To do that, a new solid-core circular PCF design with various air hole diameters and lattice constants is presented, and the design features are numerically analyzed in detail. After 40 simulations, we determined three structures that possess optimal dispersion with the following lattice constants (Ʌ) and filling factors for the first ring (d1/Ʌ): Ʌ = 0.8 µm, d1/Ʌ = 0.45 for #F1, Ʌ = 0.9 µm, d1/Ʌ = 0.45 for #F2, and Ʌ = 1.0 µm, d1/Ʌ = 0.45 for #F3. High nonlinearity and low attenuation are outstanding features of our model. With these advantages, the proposed fibers are targeted for smooth flat broadband supercontinuum generation for near-infrared applications.

Performance analysis of slotted rectangular photonic crystal fiber structures in terahertz waveguidance

For an efficient and reliable transmission of data beyond 5G and 6G technologies, proper waveguide structures are needed. We present a rectangular solid-core slotted cladding photonic crystal fiber (PCF) and analyze its signal transmission capability in the terahertz (THz) regime. The proposed PCF performances have been investigated numerically using the finite element method. Various parameters, such as birefringence, core power fraction, effective material loss, effective area, mode-field diameter, beat length, dispersion, confinement loss, etc., have been studied by varying the geometry of the PCFs. The obtained simulation results exhibit dispersion of the order 2 ns / THz / cm, high birefringence of 0.0983, low confinement loss of the order 10 − 19 mm − 1, the effective area of 0.073 mm2, and high core power fraction of 99.8% in 0.2 to 2 THz range. All the parameters have been optimized among six different structures of the proposed PCF. This analysis will be helpful for the researchers to predict the transmission capability of THz waves in a rectangular PCF waveguide, which assures the boost in communication beyond 5G toward 6G evolution.

Theoretical Analysis of The Super-Gaussian Pulse Propagation in Solid-Core Photonic Crystal Fiber

Fiber optics have been greatly enhanced by photonic crystal fibers based on microstructure air-glass designs. On the one hand, such fibers enable highly tight light confine in a small mode shape region, resulting in significantly improved alternative options between light and dielectric medium. Photonic crystal fibers, on the other hand, allow light to be guided via air cores instead of glass. As a result, the latter form of fiber decreases of optical nonlinearities in ways that classic fiber designs cannot. The chirp effect and dispersion of photonic crystal fibers with super-Gaussian pulses during various pulses durations are examined in this paper. In both normal and anomalous dispersion patterns. As done the chirp effect and fiber dispersive nonlinear effects are investigated. For this study, the mathematical model of the solution of nonlinear equation is split-step Fourier method. The peak power reduces for broad pulses. When the magnitude of the super-Gaussian pulse increasing proportion, the pulse constriction is also noticeable, Furthermore, these results disclose important facts, such as the fact that an anomalous dispersion system is superior to a regular dispersion system for pulse. These findings are incredibly useful in learning more about photonic crystal fiber and improving data speeds in modern optical communication systems.

Surface mode enhanced by avoided crossing in microstructure fibers for improved SERS sensing

Photonic crystal fibers (PCFs), providing ingenious microfluidic channels and intense light guidance, have many advantages in the detection of three-dimensional surface-enhanced Raman scattering (SERS). In solid-core PCFs, the light interacts with the sample in the form of an evanescent field, which is weak and limits the SERS detection performance. In this paper, we propose a new mechanism based on avoided crossings between the fiber core mode and the surface mode, which greatly enhances the laser power ratio in the liquid channels and improves the SERS sensitivity. Numerical results show that the intensity in the liquid channels can be increased from 2.8 % to 42 %. To realize this avoided-crossing effect in PCFs experimentally, the silver mirror reaction was optimized which can decorate discrete and densely distributed silver nanoparticles on the hydroxylated surface of the microfluidic channels in less than 15 min. The resulting SERS-active suspended-core PCF has ultra-high sensitivity, with a detection limit of 10−12 M, and an enhancement factor of 1010 for crystal violet solution. It also provides good stability and reproducibility with a relative standard deviation of 4.8 %. This ultra-sensitive and highly reproducible PCF-SERS probe has great potential for application in rapid in-situ detection.

EFFECT TWO ZERO DISPERSION WAVELENGTHS AND RAMAN SCATTERING IN THE THIRD-ORDER SOLITON OF SOLID CORE PHOTONIC CRYSTAL FIBERS TO PRODUCE SUPERCONTINUUM GENERATION

Photonic crystal fibers (PCFs) which consist of dielectric materials are a don't ever and an ever field in more modern application. The Split-Step Fourier method (SSFM) was used in this work to create a fiber photonic crystal, which was suggested and validated using a Matlab software .The impact of two -zero- dispersion on the Soliton in solid core photonic crystal fibers has been studied by investigating the interplay between Raman effect and second- order- dispersion. It has been discovered that the proposed photonic crystal fibers two –zero- dispersion wavelengths (TZDW) can be used to effectively tailor the properties of third order soliton. Many current applications, including medical and industrial, rely on spectral expansion. In addition, soliton has an important role in modern communication systems.