Elliptical-hole Photonic Crystal Fiber Research Articles

Elliptical-spiral elliptical-hole photonic crystal fiber with high birefringence, large nonlinearity, and two zero dispersion.

This paper presents a soft-glass (SF-57) elliptical-spiral photonic crystal fiber with elliptical air holes for achieving high birefringence, large nonlinearity, and tailoring two zero-dispersion wavelengths (ZDWs) in the near-infrared region. A full-vector finite-element method with perfectly matched boundary layer is used to characterize the properties of the photonic crystal fiber for different ellipticity ratios. The designed fiber has a birefringence 4 times higher than the circular-spiral structure. There are two ZDWs at around 1.2 µm and 2.8 µm which can be finely tuned depending on the ellipticity ratios along with a large nonlinearity. Due to the superior guiding properties, the proposed structure can be used for polarization control and broadband supercontinuum generation.

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.

Defected-core photonic crystal fiber magnetic field sensor based on Sagnac interferometer

A high-sensitivity magnetic field sensor based on photonic crystal fiber (PCF) Sagnac interferometer is proposed by finite element method (FEM). The elliptical-hole PCF is injected with water-based magnetic fluid. The fiber core is introduced in an elliptical hole to act as a defected core. The sensitivities are 13.25 and −14.32 nm/Oe at the wavelength of 1750 and 1780 nm, respectively, as the magnetic field H is 100 Oe. The simulation result shows that the sensitivity is extremely high near the wavelength of 1765 nm, because the group birefringence Bg is about zero at that wavelength. The above theory is examined in a different configuration by the transmission mode. The average sensitivities are 0.265, 1.63 and −1.915 nm/Oe, respectively, for the dip wavelength A, B and C as the fiber length is 5 cm. The detecting window is 60Oe. We also demonstrate that the sensitivity can be greatly enhanced by 1–2 orders of magnitude by introducing a defected core.

High birefringence rectangular-hole photonic crystal fiber

A novel highly birefringent photonic crystal fiber (PCF) based on rectangular-hole is proposed and numerically analyzed by employing the finite-element method. The proposed PCF can achieve birefringences similar to those of the elliptical-hole PCF and rhombic-hole PCF. The properties of such PCFs are investigated for different parameters related to rectangular-holes, including the rectangular-hole pitch, length and the length and width ratio. The results show that the birefringence of rectangular-hole PCF reaches the magnitude of 10−3 which fulfills the requirements of high precision applications in optical systems, which will find application in nonlinear optics.

Characteristics analysis of extruded elliptical hole photonic crystal fibers with square air-core

An extruded elliptical hole photonic crystal fibers PCF with square air-core is proposed. By using a full vector finite-element method FV-FEM and anisotropic perfectly matched layers APML, the structure and optical properties of the proposed PCF are analyzed. Simulation results show that the birefringence of the proposed photonic crystal fiber can be up to the order of 10−2, and has a flattened dispersion from 1.20μm to 1.80μm. The proposed PCF may have important application in super-continuum SC generation, dispersion compensation, fiber-optic sensing systems and other aspects.

Highly Birefringent Extruded Elliptical-Hole Photonic Crystal Fiber

Highly birefringent extruded elliptical-hole photonic crystal fibers (PCFs) with single defect and double defect are proposed and investigated, which are supposed to be achieved by extruding conventional triangular-lattice circular-hole PCFs. Comparative research on the birefringence and the confinement loss of the proposed PCFs with single defect and double defect is presented. Simulated results show that the proposed extruded elliptical-hole PCFs with single defect and double defect can be with high birefringence up to the order of 10-2. Confinement loss increases when the ellipticity of the air hole of the proposed PCFs increases, which nevertheless can be overcome by increasing the ring number or the area of the air holes in the fiber cladding.

Dependence of birefringence on elliptical-hole orientation in photonic crystal fibers

In this paper, the dependence of birefringence on the orientation of elliptical holes in triangular-lattice elliptical-hole photonic crystal fibers (PCFs) is investigated numerically. A resonant enhancement of birefringence between the anisotropic lattice arrangement and oriented elliptical holes is observed, and the birefringence varies periodically with the ellipticalhole orientation. When the major axes of adjacent elliptical holes are parallel, the birefringence approaches the maximum. Based on the numeric analysis, a novel highly birefringent PCF is proposed, and the maximum modal birefringence of 0.086 is achieved.

Analysis of birefringent and dispersive properties of photonic crystal fibers

Two types of high birefringence photonic crystal fiber (PCF) which import four or six big circular air holes near the elliptical-hole are proposed. Their birefringent and dispersive properties are analyzed by full-vector finite-element method (FEM). Numerical analysis demonstrates that importing the big circular hole near the center of elliptical-hole PCFs can achieve a high birefringence. When the ratio (d/Λ) of diameter to hole spacing is larger than 0.8, the proposed two types of PCF have a larger birefringence than that of sole elliptical air hole ones. When the ratio d/Λ is equal to 0.95, the birefringences of these two types PCF can be as high as 4.27×10(-3) and 5.09×10(-3) at the wavelength of 1.55 μm, respectively. Besides, PCF with the four big circular air holes has a large negative dispersion at the long wavelength in x-polarized mode, which indicates a potential in single-polarized mode dispersion compensation.

矩形孔光子晶体光纤

By employing a full-vector finite-element method and anisotropic perfectly matched layers,a novel rectangular-hole photonic crystal fiber is fully investigated and a method to achieve high birefringence of the photonic crystal fiber is proposed.Simulation results show that birefringence property of the rectangular-hole photonic crystal fibers is almost the same as the elliptical-hole photonic crystal fiber which can achieve the high birefringence up to the order of 0.01.Both the rectangular-hole photonic crystal fiber and the elliptical-hole photonic crystal fiber have the similar properties such as the mode profile,birefringence,confinement loss and so on.

High birefringent rhombic-hole photonic crystal fibers

High birefringence induced by rhombic air-hole photonic crystal fibers (PCFs) is numerically analyzed by using the finite-element method. The birefringence of a few kinds of PCFs was investigated with different parameters related to rhombic holes, including the rhombic-hole shape, size, and spacing. It was found that the birefringence of the proposed rhombic-hole PCF in this study is relatively larger than that of an elliptical-hole PCF with the same air-filling fraction (f=0.0375) when the ratio of the rhombic-hole diagonal length is equal to the elliptical-hole ellipticity.

Highly birefringent photonic crystal fiber based on a double-hole unit

We propose a novel highly birefringent photonic crystal fiber (PCF) based on a double-hole unit. Because of the effect of the double-hole unit in which double airholes can be effectively viewed as elliptical airholes, the proposed PCF can achieve birefringence similar to that of an elliptical-hole PCF with high birefringence even up to the order of 0.01 and still avoid the inherent challenge to fabricate an elliptical-hole PCF. The proposed PCF also has a lower confinement loss than an elliptical-hole PCF with the same air-filling fraction.

Low-dispersion high-birefringence effect of squeezed hexagonal lattice elliptical hole photonic crystal fiber

A new type of photonic crystal fiber for realizing the effect of low dispersion high birefringence is proposed. The fiber is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air-hole along the fiber length. Dispersion and birefringence are investigated simultaneously by using the full vectorial plane wave method. Simulations indicate that the wavelength for realizing low-dispersion high-birefringence can be controlled by artificially choosing the structure parameters of photonic crystal fiber, such as the hexagonal lattice squeezing ratio, the relative air hole spacing and the air hole ellipticity. The optimal and feasible parameters of the fiber with low-dispersion high-birefringence are given, with the result of the total dispersion being within ±5 ps·nm-1km-1 over an ultra broad wavelength range from 1360 to 1670 nm and the corresponding high birefringence being about 15×10-2 at 1550 nm.

单缺陷和双缺陷的高双折射压缩型椭圆孔光子晶体光纤

Highly birefringent elliptical-hole photonic crystal fibers (PCFs) with single defect and double defects are proposed, which are supposed to be achieved by extruding normal circular-hole PCFs based on a triangular-lattice photonic crystal structure. Comparative research on the birefringence and the confinement loss of the proposed PCFs with single defect and double defects is presented. Simulation results show that the proposed PCFs with single defect and double defects can be with high birefringence (even up to the order of 10^{02}). The confinement loss increases when the ellipticity of the air hole of the PCFs increases, which nevertheless can be overcome by increasing the ring number or the area of the air holes in the fiber cladding.

Highly Birefringent Elliptical-Hole Photonic Crystal Fibers With Double Defect

A novel elliptical-hole photonic crystal fiber (PCF) with double defect is theoretically investigated, and its high birefringence [including both the phase-index birefringence (PIB) and the group-index birefringence (GIB)] is demonstrated, which can reach an order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> Such a PCF can especially have a very high PIB, with a negligible GIB in a small band of normalized frequencies. The PIB of this PCF is much higher than that of the circular-hole PCF with double defect, under comparable parameters. Compared with the elliptical-hole PCF with single defect, the present PCF possesses the advantages of both a higher PIB and a larger modal area for modest ellipticities; thus, it is more suitable in linear applications, as well as in fabrication. Moreover, a novel single-polarization single-mode (SPSM) PCF with a broad wavelength band is proposed and demonstrated. In addition, a new approach in designing broadband SPSM PCFs is suggested.

Highly birefringent elliptical-hole photonic crystal fiber with squeezed hexagonal lattice

We propose a novel polarization-maintaining index-guiding photonic crystal fiber (PCF). It is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air holes. Using a full-vector finite-element method, we study the modal birefringence of the fundamental modes in such PCFs. Numerical result shows that very high modal birefringence with a magnitude of the order of 10(-2) around 1550 nm has been obtained. Furthermore, large normal dispersion appears over a wide range of wavelengths in both orthogonal polarizations.

Ultrahigh Birefringent Photonic Crystal Fiber With Ultralow Confinement Loss

A photonic crystal fiber (PCF) with circular air holes in the fiber cladding and elliptical air holes in the fiber core is proposed. According to calculation, both ultrahigh birefringence (larger than 0.01) and ultralow confinement loss (less than 0.001dB/km) can be achieved simultaneously over a large wavelength range for a PCF with only four rings of circular air holes in the fiber cladding. The confinement loss in this PCF can be effectively reduced while the birefringence almost remains the same. The proposed design of the PCF is a solution to the tradeoff between the birefringence and the confinement loss for the originally reported highly birefringent elliptical-hole PCF. Moreover, an approach to modify the effective index of fiber core is also suggested in this letter

Localized orthogonal function model of elliptical-hole photonic crystal fibers

A novel model for light propagation in elliptical-hole photonic crystal fibers (PCFs) is developed in terms of orthogonal function model. A new method for constructing supercell lattice is proposed; with this method the transverse index profile is decomposed into two periodic structures, and the mode field is decomposed using Hermite-Gaussian functions. The propagation constant and the mode field distribution of the PCF can be calculated by recasting the Maxwell equations into on eigenvalue system. With this model, the mode properties including dispersion properties, polarization properties and mode area can be analyzed for circular or elliptical hole PCF.

Mode disorder in elliptical hole PCFs

In the elliptical-hole photonic crystal fibers, when the central defect air hole is large enough, the modes will be disordered. The order of the HE 11-like mode is investigated in detail based on the full vector supercell overlapping method. The degeneracy will be enhanced at the frequency where the modes begin to be disordered.

Dependence of mode characteristics on the central defect in elliptical hole photonic crystal fibers

Some mode characteristics are obtained by the full vector supercell overlap method that has been developed to model triangular lattice elliptical hole photonic crystal fibers regardless of whether the light is guided by total internal reflection or a photonic bandgap mechanism. When the central defect hole is large enough, the modes are disordered. Birefringence (Deltan) dependence on the central defect is discussed in detail by numerical analysis.

Polarization and dispersive properties of elliptical-hole photonic crystal fibers

We survey the properties of photonic crystal fibers with elliptical air holes, examining mode shapes, birefringence, group velocity walkoff and dispersion, and cutoff conditions. We find new types of behavior for each quantity and demonstrate the possibility achieving large birefringence with zero walkoff in the single-mode regime. We show that the dispersive properties of the vector modes are closely tied to those of the so-called fundamental space filling modes, and that at long wavelengths, the fibers exhibit a single-polarization single-mode regime of propagation without the presence of material anisotropy.