Low Confinement Loss Research Articles

Octagonal dual-concentric-core photonic crystal fiber for C-band dispersion compensation with low conf inement loss

A novel kind of octagonal dual-concentric-core photonic crystal fiber (PCF) is calculated with the finite element method (FEM) and proposed for broadband compensation. In order to realize highly negative dispersion, the hole diameter of the second ring is reduced relative to conventional PCFs. Numerical simulation results show that when the diameters of large holes and small holes are 0.77 \mu m and 0.5 \mu m, respectively, and the pitch of the adjacent rings is 1.1 μm, the negative dispersion can achieve about –840 ps.nm-1.km-1 at 1 550 nm and the dispersion slope can match with single mode fiber (SMF-28) perfectly. This PCF can compensate the positive dispersion and also its slope of about 50 times its length of SMF-28 fiber, which is suitable for C-band optical fiber telecommunication as a dispersion compensation fiber.

Photonic Crystal Fiber With an Ultrahigh Birefringence and Flattened Dispersion by Using Genetic Algorithms

We developed a high-throughput technique to design photonic crystal fiber (PCF) structures with desired properties and functionalities. By using a genetic algorithm, a high birefringence and an ultra-flattened chromatic dispersion over a large wavelength range are achieved. It is shown that a low confinement loss can be obtained while the birefringence remains the same. The numerical results show that the presented PCF structure can be successfully employed as maintaining polarization devices working in a large zero- chromatic dispersion region.

基于微结构纤芯的超低损耗多零色散点的高双折射光子晶体光纤

基于微结构纤芯的超低损耗多零色散点的高双折射光子晶体光纤

Highly birefringent polymer terahertz fiber with honeycomb cladding

Two highly birefringent polymer terahertz (THz) fibers were proposed in this paper, which were formed with honeycomb cladding and some elliptical air holes in the fiber core. The losses and mode birefringence of two different fibers are investigated by finite-different time-domain method. The results show that fiber 2 can achieve both high birefringence (larger than 0.022) and low confinement loss (0.01dB/m) in a wide THz frequency range. Moreover, compared with a round solid-core fiber, guiding loss of the THz fiber caused by polymer material absorption can be reduced effectively as a part of the mode power is trapped in the air holes.

Highly Birefringent Elliptical-Hole Microstructure Fibers With Low Confinement Loss

A novel kind of elliptical-hole highly birefringent microstructure optical fibers (MOFs) with two defects and six rings is analyzed and proposed. Simulation results show that geometrical birefringence of this elliptical-hole MOF is two times higher than that of the circular-hole ones, which found to be about 3.5×10-3. The polarization beat length of such fiber is calculated to be 0.44 mm. Besides, this kind of MOF with two defects can couple with single mode fibers efficiently and the confinement loss is almost near zero when the cladding ring number reaches 6. Such proposed fiber with high birefringence and low confinement loss can find really potential applications in the fields of light transmission and optical sensing.

Low confinement loss hybrid-guiding tellurite photonic bandgap fiber

A hybrid-guiding tellurite (TZNLP) photonic bandgap fiber (PBGF) with low confinement loss is presented in this paper. A detailed comparison between the hybrid-guiding tellurite PBGF in which the high-index rods (TLWMN) replace one row of air holes in the radial direction and the all-solid tellurite PBGF has been accomplished. Low confinement loss windows can be achieved in this novel fiber due to the collaborated action of two guiding mechanisms–total internal reflection and antiresonant reflection.

High birefringent rectangular-lattice photonic crystal fibers with low confinement loss employing different sizes of elliptical air holes in the cladding and the core

Based on the full-vector finite element method with anisotropic perfectly matched layers, modal birefringence and confinement loss for the fundamental mode in rectangular-lattice photonic crystal fibers with different sizes of elliptical air holes in the cladding and the core are investigated numerically. The results show that the modal birefringence in this proposed photonic crystal fibers can be up to 5.64×10−2 at the wavelength of 1.55μm. Moreover, when the birefringence is higher than 4×10−2, the confinement loss of x-polarized mode can be kept less than 0.005dB/km at 1.55μm. It means that the tradeoff between the high birefringence and the low confinement loss is overcome.

Demonstration of Ultra-Flattened Dispersion Low Confinement Loss in Square Lattice Structure Photonic Crystal Fibers

Demonstration of Ultra-Flattened Dispersion Low Confinement Loss in Square Lattice Structure Photonic Crystal Fibers

Generation of hollow beam from photonic crystal fiber with an azimuthally polarized mode

A kind of photonic crystal fiber (PCF) with an azimuthally polarized (TE01) mode is proposed to generate hollow beam (HB). The finite element method (FEM) is employed to study the polarization properties of the fiber and normalized intensity of the HB. Simulation results show that the TE01 mode with a low confinement loss in this kind of fiber can provide a high quality HB. By varying arrangement of air holes in the cladding region or changing structure parameters of the PCF, HB of different sizes can be obtained. The smallest dark spot size (DSS) and the narrowest width of HB achieved are about 1μm and 1.4μm at a wavelength of 1.55μm, respectively. This kind of PCF, which can generate HB with an azimuthally polarized mode, has great significance in the technique of optical tweezers.

Investigation of phase birefringence and group birefringence of square size photonic crystal fiber at wavelength 1.3 μm

A new variety of square size photonic crystal fiber with high phase birefringence and group birefringence is investigated successfully via Full-Vector Finite Element Method (FV-FEM). By taking suitable geometrical fiber parameters in cladding region of solid core PCF such as elliptical air hole diameter with ellipticity a/b=0.50 and pitch 2.3μm, phase birefringence 1.0×10−3 and group birefringence 1.9×10−3 with low confinement loss 3.7×10−6dB/km are found at 1.3μm wavelength.

Doped-Core Octagonal Photonic Crystal Fiber with Ultra-Flattened Nearly Zero Dispersion and Low Confinement Loss in a Wide Wavelength Range

In this article, an octagonal photonic crystal fiber is proposed, in which the core region and four air holes in the inner ring have a refractive index of 1.43. Compared with the hexagonal photonic crystal fiber, the octagonal photonic crystal fiber has less confinement loss. To study the propagation characteristics of the proposed photonic crystal fiber, the finite-difference time-domain method with perfectly matched layer boundary conditions has been used. By properly optimizing the design parameters of the proposed octagonal photonic crystal fiber, an ultra-flattened nearly zero dispersion of 0 ± 0.1 ps/nm.km in the wavelength range of 1.25 μm to 1.65 μm is made feasible, and for wavelengths shorter than 1.65 μm, confinement losses of less than 7 × 10−7 dB/km have been achieved.

Ultra low bending loss equiangular spiral photonic crystal fibers in the terahertz regime

An Equiangular Spiral Photonic Crystal Fiber (ES-PCF) design in Topas® for use in the Terahertz regime is presented. The design shows ultra low bending loss and very low confinement loss compared to conventional Hexagonal PCF (H-PCF). The ES-PCF has excellent modal confinement properties, together with several parameters to allow the optimization of the performance over a range of important characteristics. A full vector Finite Element simulation has been used to characterize the design which can be fabricated by a range of techniques including extrusion and drilling.

Design of Highly Birefringent and Low Confinement Loss Photonic Crystal Fibre by Introducing Asymmetric Defect Structures

Photonic crystal fibres –micro structured fibre consisting of air hole arrays running along its lengthhave attracted much attention for fibre device application because of its unusual optical properties that are not realized in standard optical fibre, such as high birefringence, high nonlinearity, low confinement loss and tailorable chromatic dispersion. High birefringent PCF can be designed by breaking the circular symmetry and implementing asymmetric defect structures such as dissimilar air hole diameter, varying the number of circular and elliptical air holes. This paper proposes a highly birefringent PCF with ultra-low confinement loss by introducing four ring solid core hexagonal structure which having both elliptical and circular air holes and introducing large air hole diameters near the core region for making the asymmetry. The modal birefringence, refractive indices, confinement loss and chromatic dispersion are calculated by using Finite element method (FEM). An endlessly single mode, high birefringent (05.152x10) and a low confinement loss (7.85x10 dB/km) found at the excitation wavelength of λ=1550nm with only four rings of air holes in the fiber cladding.

Highly nonlinear all-solid photonic crystal fibers with low dispersion slope

A fluorine-doped trench-assisted structure is proposed to improve the nonlinearity of photonic crystal fibers (PCFs). Three all-solid highly nonlinear PCFs with low dispersion slope and low confinement loss are designed. They exhibit all normal dispersion, two zero dispersion wavelengths (ZDWs) and one ZDW just at 1.55 μm, respectively. The lowest dispersion slope is 5.12×10(-4) ps/(km·nm(2)), which is 2 orders of magnitude lower than that of conventional highly nonlinear fibers. A nonlinear coefficient of 31.5 W(-1)·km(-1) and low loss of 9.62×10(-5) dB/km at 1.55 μm has been achieved for this PCF.

Design of highly nonlinear dispersion flattened hexagonal photonic crystal fibers for dental optical coherence tomography applications

In this paper, we propose a highly nonlinear dispersion flattened hexagonal photonic crystal fiber (HNDF-HPCF) with nonlinear coefficients as large as 57.5W−1 km−1 at 1.31 μm wavelength for dental optical coherence tomography (OCT) applications. This HNDF-HPCF offers not only large nonlinear coefficient but also very flat dispersion slope and very low confinement losses. Using these characteristics of our proposed PCF, it is shown through simulations by using finite difference method with an anisotropic perfectly matched boundary layer that this PCF offers the efficient supercontinuum (SC) generation for dental OCT applications at 1.31 μm wavelength using a picosecond pulse easily produced by commercially available less expensive laser sources. Coherent length of light source using SC is found 10 μm and the spatial resolutions in the depth direction for dental applications of OCT are found about 6.1 μm for enamel and 6.5 μm for dentin.

Elliptical defected core photonic crystal fiber with high birefringence and negative flattened dispersion

We propose a novel design of photonic crystal fiber (PCF) using an elliptical air hole in the core as a defected core in order to enhance the performance of modal birefringence and to control the properties of chromatic dispersion at the same time. From the simulation results, it is shown that the proposed fiber has high birefringence up to the order of 10(-2), negative flattened chromatic dispersion in a broad range of wavelengths, and low confinement loss less than that of the single mode fiber. The outstanding advantage of the proposed PCF is that high birefringence, negative flattened dispersion, and low confinement loss can be achieved just by adding a small sized elliptical air hole in the core to the elliptical air hole PCF, especially at the same time.

Ultra-flattened dispersion hexagonal photonic crystal fibre with low confinement loss and large effective area

In this study, a new photonic crystal fibre (PCF) structure is proposed which is suitable for optical telecommunications. This PCF has some features including low- and ultra-flattened dispersion and low confinement loss as well as a large effective area in a wide range of wavelengths. To analyse this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers boundary conditions has been used. For the proposed PCF, dispersion has small variations about 0.8 ps/(nm km) in the wavelength range from 1.1 to 1.7 m and dispersion value is less than 2.5 ps/(nm km) in applicable wavelengths. The confinement loss is obtained less than 10 -6 dB/km in this range, whereas the effective area is around 61.2 m 2 at 1.55 m wavelength. The results show that the confinement loss of the designed hexagonal PCF is small, although the effective area is large. The optimal structural parameters are designed to achieve minimum confinement loss, dispersion and dispersion variation which can be properly utilised in broadband optical transmission applications.

Nearly zero-dispersion, low confinement loss, and small effective mode area index-guiding PCF at 1.55 μm wavelength

In this paper, a new simple structure of index-guiding photonic crystal fiber (PCF) is designed and presented. In this PCF, dispersion, confinement loss, and effective mode area characteristics are investigated in the second communication window (1.55 μm). Since 1.55 μm wavelength is widely used in optical communication systems, we try to optimize the PCF characteristics in this wavelength by designing an index-guiding PCF and three versions of optimized PCF. The results show that the dispersion is obtained very close to zero around 4.6×10−4 ps/(nm·km). Also, the confinement loss is 2.303×10−6 dB/km and effective mode area is as small as 2.6 μm2.

Comparative study of fundamental properties of honey comb photonic crystal fiber at 1.55µm wavelength

Fundamental properties such as mode field distribution, real effective refractive index, imaginary effective refractive index, confinement loss of two new kinds of honeycomb photonic crystal fibers are successfully studied by using Full-Vectorial Finite element method (FV-FEM). Low confinement loss 0.1×10-4dB/km is achieved at wavelength 1.55µm in hollow core honey comb PCF by removing 6-air holes in cladding region with air hole diameter 1.38µm in cladding region, pitch 2.3µm and air core diameter 0.2µm.

Characteristics analysis of photonic crystal fiber with rhombus air-core

Aiming at the requirement of low confinement loss and multiple zero dispersion points in fiber-optic sensing systems and optical communication networks, a new type of photonic crystal fiber (PCF) with rhombus air-core is proposed. By using finite element method (FEM), the structural and optical properties of the proposed PCF are analyzed. Simulation results reveal that the proposed PCF has lower confinement loss with 10−3dB/m and higher birefringence. Besides, two zero dispersion points can be obtained after optimization. The proposed PCF may have important applications in fiber-optic sensing systems and other aspects.