Circular Photonic Crystal Fiber Research Articles

Fiber design and performance analyses for optical multiplexing: terahertz optical communications

Multiplexing is the process of combining multiple signals at a single channel. Orbital Angular Momentum (OAM) is one of the main multiplexing techniques for optical data transmissions. This paper examines and suggests a hollow core with four layers of semilunar air-hole-shaped circular photonic crystal fiber (PCF) capable of transmitting terahertz (THz) OAM information-carrying modes. By using the full vector finite element method (FEM), OAM multiplexing is analyzed for the proposed fiber. All the THz OAM-based factors are analyzed at a frequency band ranging from 400 GHz to 800 GHz. For the first time, some important PCF factors such as effective refractive index difference (ERID), dispersion profile (DP), OAM purity, confinement loss (CL), effective mode area (ERA), and numerical aperture (NA) are quantitatively discussed with applications. The proposed design supports 50 OAM modes with ERID up to 10−3. The PCF has a CL of approximately 10–10 dB cm−1 and the lowest dispersion profile is 0.3581 ps/THz/cm. Furthermore, the OAM purity is around 97%. Nonetheless, the proposed design can be used in THz-OAM transmission and high optical fiber communications.

Circular lattice benzene-core PCFs with flat near-zero dispersion for low-power broad-spectrum supercontinuum generation

A circular photonic crystal fiber infiltrated with benzene with different air-hole diameters is proposed as a new supercontinuum light source. Optical properties related to dispersion, effective mode area, nonlinear coefficient, and attenuation of the fundamental mode are investigated numerically. Two optimized structures are selected and verified against supercontinuum generation (SCG) in detail. The first structure (#F1) possesses all-normal dispersion, while the second (#F2) has a zero-dispersion wavelength. The possibility of coherent, octave-spanning SCG is proved by a 40 fs pulse, 1.064 μm wavelength, and 0.45 kW of power in-coupled into the core of #F1. Otherwise, injecting a 90 fs duration, 1.5 μm wavelength, and 0.555 kW peak power pump pulse into #F2 generates a broad SC spanning 0.76–4.23 μm. With the advantages of flat near-zero dispersion, high nonlinearity, low attenuation, and low input power used for SCG, the proposed fibers may lead to new low-cost all-fiber optical systems.

Numerical Investigation of Optical Properties in Carbon Tetrachloride-Filled Photonic Crystal Fibers

In this work, we design circular lattice photonic crystal fibers using Lumerical Mode Solution software, its hollow core filled with carbon tetrachloride. Optical properties including effective refractive index, chromatic dispersion, nonlinearity, and fiber loss were investigated numerically in detail based on solving Maxwell's wave equations. The small effective mode areas of only a few µm2, and confinement loss as low as 14.799 dB/m at specific pump wavelengths were obtained. It was found that near-zero ultra-flattened chromatic dispersion with fluctuations of ±0.44 ps/nm.km spans from 1300 to 1830 nm. Three photonic crystal fibers with optimal structure and features were suggested for broadband supercontinuum generation orientation.

Optical properties of circular photonic crystal fibers filled with carbon tetrachloride

In this work, the dispersion properties and nonlinear properties of circular photonic crystal fibers were improved by a combination of carbon tetrachloride infiltration into the core and modification of the air hole diameters d1 and d2 of rings in the cladding. The quantities such as dispersion, effective mode area, nonlinear coefficient, and low confinement are analyzed in detail. Based on the survey results, two photonic crystal fibers with optimal optical properties were proposed which are beneficial for supercontinuum generation. The first fiber with Ʌ = 1.0 µm, d1/Ʌ = 0.6, has an all-normal dispersion of –10.785 ps/nm.km at a pump wavelength of 0.985 µm. The high nonlinear coefficient of 581.795 W–1.km–1 and the low confinement loss of 3.904 dB/m are also achieved with this fiber. SC broadband under the influence of soliton is expected to be generated when using the second fiber (Ʌ = 2.0 µm, d1/Ʌ = 0.3) with flat and low anomalous dispersion at the pump wavelength of 1.3 µm.

Design of New Photonic Crystal Fiber for Orbital Angular Momentum Modes Transmission

In order to achieve the flexibility and miniaturization of orbital angular momentum (OAM) fiber coupler, it is necessary to continuously design and optimize the base fiber to cooperate with the efficient transmission of multiplexed beam. It is more advantageous to use the photonic crystal fiber (PCF) instead of ring fiber in the coupler design. We have proposed a new fiber based on circular PCF structure to support high performance OAM modes transmission. The optimal parameters are selected to realize the stable transmission of 4 OAM mode groups with high mode quality. In the wavelength range of 1.2 μm∼2.0 μm, the confinement loss of low order mode is less than 10−8 dB/m, and the mode purity is more than 81.7%. Because of its flexible structure and low loss characteristics, the proposed OAM fiber can be widely used in the design of optical fiber devices in modular division multiplexing (MDM) communication systems.

A novel graphene-based circular dual-core photonic crystal fiber pressure sensor with high sensitivity

A novel graphene-based circular dual-core photonic crystal fiber pressure sensor with high sensitivity

Supercontinuum spectra above 2700 nm in circular lattice photonic crystal fiber infiltrated chloroform with the low peak power

Supercontinuum spectra above 2700 nm in circular lattice photonic crystal fiber infiltrated chloroform with the low peak power

Design and analysis of a hexagonal circular photonic crystal fibre with ultra-high negative dispersion and low confinement loss

This paper proposes a Hexagonal Circular Photonic Crystal Fiber (HC-PCF) with uniform tiny air holes around the core, obtaining ultra-high negative dispersion, high Birefringence and low confinement loss. The modal properties of the HC-PCF are investigated using the full-vectorial-Finite Element Method (FEM) with a perfectly matched layer as the boundary condition. The numerical investigations show ultra-high negative dispersion of −25503 ps/nm.km, a birefringence of 1.36×10-2, a nonlinearity of 38.34w-1km-1 and a confinement loss of 4.95×10-3 dB km-1 at the wavelength of 1550 nm. Moreover, the proposed HC-PCF exhibits a high negative dispersion and multiple Zero Dispersion within the 800 to 2000 nm wavelengths range. Specifically, the high negative dispersion, low optical Confinement Loss, and multiple Zero Dispersion Wavelengths (ZDW) give the proposed HC-PCF high Power Spectral Density (PSD). These characteristics make the proposed fibre suitable for long-range telecommunication networks and optical sensing.

Design and numerical analysis of a circular SPR based PCF biosensor for aqueous environments

This paper presents the design and numerical analysis of a circular photonic crystal fiber (PCF) biosensor based on surface plasmon resonance (SPR) for aqueous environments. The proposed biosensor has a geometrical design that uses the cladding at the fiber's exterior to simplify the gold and analyte deposition process. The sensing characteristics and performances of the proposed biosensor are fully investigated with the finite element method. The investigation indicates that the plasmonic material's thickness affects the biosensor's performance. The results of the proposed biosensor demonstrate a wide refractive index range of 1.30 to 1.44, with the highest wavelength or spectral sensitivity as 21,000 nm/RIU and the highest resolution as 9.09×10−6 RIU. The proposed biosensor has a straightforward geometric profile. The proposed biosensor is stable and suited for aqueous surroundings and wide-range detection applications.

High-performance surface plasmon resonance fiber sensor based on cylindrical vector modes

Cylindrical vector modes with azimuthal polarization and low transmission loss are proposed for the first time to be utilized in a novel design of a surface plasmon resonance (SPR) sensor based on a circular photonic crystal fiber (C-PCF). A C-PCF with a ring of air holes in the cladding is designed where a gold layer with a thickness of 44 nm is coated on the outer cladding surface. The optimal geometric parameters are determined using the finite-element method (FEM) for a high-quality TE01 mode and high sensitivity of the sensor. The proposed SPR sensor shows high sensitivity for analyte refractive index (RI) ranging from na = 1.29 to 1.34 over the wavelength range of 1400–2000 nm. It is expected that the proposed sensor can sense low concentrations of hemoglobin, lymphocytes and monocytes of red and white blood cells which are effective in diagnosing the progress of cancer tumors. The maximum sensitivity of 13,800 nm/RIU is obtained in the refractive index environment of 1.33–1.34. The sensor resolution is of the order of 10−6 and the amplitude sensitivity reaches its maximum of 2380 RIU−1 at na = 1.30 which is the highest value ever reported. Our proposed sensor shows high sensitivity and simultaneously simple design with high performance.

Flat-top and broadband supercontinuum generation in CCl4-filled circular photonic crystal fiber

In this work, a flat-top and broadband supercontinuum (SC) generation in photonic crystal fibers (PCFs) infiltrated with carbon tetrachloride (CCl[Formula: see text] with different air hole diameters in the cladding has been introduced. The optical properties of the fundamental mode are analyzed by numerical simulation. Based on the obtained results, two optimized PCFs with small dispersion are proposed and verified against SC generation in detail. The first fiber has an all-normal dispersion of [Formula: see text]9.376[Formula: see text]ps.nm[Formula: see text].km[Formula: see text] at the pump wavelength of 0.98[Formula: see text][Formula: see text]m, generating broadband of 768[Formula: see text]nm and flat-top with only 0.3[Formula: see text]nJ of input energy and time duration of 90[Formula: see text]fs. In the meantime the dispersion property of the second fiber is anomalous, which equals 1.105[Formula: see text]ps[Formula: see text][Formula: see text][Formula: see text]nm[Formula: see text][Formula: see text][Formula: see text][Formula: see text]km[Formula: see text] at 1.3[Formula: see text][Formula: see text]m pump wavelength. The second fiber generates a SC spectrum of 1,751.1[Formula: see text]nm with input energy and time duration of 0.55[Formula: see text]nJ and 55[Formula: see text]fs, respectively. Proposed fibers are suitable for all-fiber SC sources which could lead to new low-cost all-fiber optical systems.

An ultra-flattened chromatic dispersion in circular C6H6-infiltrated photonic crystal fibers

An ultra-flattened chromatic dispersion in circular C6H6-infiltrated photonic crystal fibers

Effect of the Temperature and the Geometrical Parameters on the Modal Properties of Circular Photonic Crystal Fiber

Effect of the Temperature and the Geometrical Parameters on the Modal Properties of Circular Photonic Crystal Fiber

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 Optical Features of Circular Photonic Crystal Fibers with Various Air-hole Size

: In this workwe proposed a newly designed photonic crystal fiber (PCF) with a circular lattice, the difference between the air-hole diameters of the first ring and the other rings makes it possible to improve the nonlinear properties of fibers.  We investigated the effect of varying the filling factor (d1/Ʌ) and lattice constant (Ʌ) on the nonlinear characteristics of photonic crystal fibers in the 0.5 - 2 µm wavelength range. The advantages of these photonic crystal fibers are the flat and near-zero dispersion, low attenuation, and high nonlinear coefficient. From simulation results, we have selected three optimal structures (Ʌ = 1.0 μm; d1/Ʌ = 0.4, Ʌ = 0.8 μm; d1/Ʌ = 0.6, and Ʌ = 0.8 μm; d1/Ʌ = 0.65) to analyze the nonlinear characteristics at the pump wavelengths. The proposed fibers are valuable for supercontinuum generation.
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Ultrabend resistant circular photonic crystal fiber design for cancer diagnosis by Raman spectrometer

One of the ways to diagnose cancer in its early stages, which can lead to timely treatment, is to use Raman spectroscopy. The Raman spectrum of a material is created by the interaction of light with the material; it determines the exact characteristics and properties of the material, which can be used to distinguish cancerous cells from healthy ones. However, the intensity of this spectrum is weak, and the optical fibers used in these devices must have very little loss and thus have low sensitivity to bending. This paper proposes a circular photonic crystal fiber with a structure in which the losses in different bending radii are significantly reduced. The modified state of the fiber at the wavelength of 1.55 μm supports the transmission of 10 modes propagated in the core. The loss for the fundamental mode at this wavelength and bending radius of 2 mm equals 3.82 × 10 − 16 dB / m, which is considered a low value. As the bending radius decreases further, low-order modes diminish, which are more sensitive to bending than high-order modes. However, their losses are lower than in high-order modes. The critical bending radius for this fiber, with the loss reaching 0.1 dB / m, is equal to 0.096 mm. This low critical bending radius shows the low sensitivity of the proposed fiber to bending. The fiber was examined in different bending radii and wavelengths, and the parameters of this structure were presented for the lowest bending losses, which can be used in Raman spectrometers as spectrum collecting fibers and improve cancer diagnosis devices with Raman spectrum.

Highly coherent supercontinuum generation in circular lattice photonic crystal fibers using low-power pulses

Two structures of circular lattice Photonic Crystal Fibers (PCFs) based on Ge20Sb15Se65 (GSS) material have been proposed for a highly coherent broadband supercontinuum generation (SCG) in the mid-infrared region. Numerical studies using the Finite Difference Eigenmode (FDE) solver on both structures show that the fundamental modes are well confined in the core while the confinement losses are very low. Also, the high nonlinear coefficient of 22.01 W−1m−1 and 17.99202 W−1m−1 for the two structures ensure that these structures can accomplish high nonlinear activity. It has been found that broadband supercontinuums (SCs) spanning from 0.45 μm to 5.3 μm and 0.48 μm to 6.5 μm can be generated using a hyperbolic secant pulse of 0.5 kW. The proposed structures also show very good structural tolerance to optical properties that prevents any radical shift in SC spectra owing to potential fabrication mismatch.

Comparison of effective mode area and confinement loss of chloroform-core photonic crystal fibers with circular and hexagonal lattices

In this research, new circular and hexagonal photonic crystal fibers (PCFs) filled with chloroform have been designed considering the difference in air hole diameters to optimize the characteristics of the fiber simultaneously. Effective mode area and confinement loss of five PCFs with optimal dispersion have been further studied to find the fiber with a great application value for supercontinuum generation (SCG). Generally, circular PCFs are dominant over hexagonal lattices because of their small effective mode area, low loss, and small dispersion. #CF1 fiber with a lattice constant (Ʌ) of 1.0 μm and filling factor (d1/Ʌ) of 0.65 has an all-normal dispersion with a low value of -1.623 ps/nm/km, a small effective mode area of 1.43 µm2, and a low loss of 2.472 dB/m at 0.945 µm. The effective mode area and confinement loss of #CF2 (Ʌ = 1.0 µm, d1/Ʌ = 0.7) are the smallest of proposed PCFs. #HF1 fiber (Ʌ = 1.0 µm, d1/Ʌ = 0.5) has a very flat dispersion curve in the 1-2 µm wavelength range and a rather small effective mode area. These are the most optimal fibers for two types of lattices, which are very suitable for near-infrared SCG.

Design of circular photonic crystal fiber for OAM extraction SDM applications

Design of circular photonic crystal fiber for OAM extraction SDM applications

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.