Single-polarization Single-mode Photonic Crystal Fiber Research Articles

A Single-Polarization Single-Mode Photonic Crystal Fiber with Four Lines of Small Elliptical Air-Holes

We present a novel single-polarization single-mode photonic crystal fiber (SPSM-PCF) design with four lines of small elliptical air-holes in order to obtain wider bandwidth for SPSM operation. The characteristics of the proposed SPSM-PCF are studied by using a full-vector finite element method (FEM) with perfect matched layer (PML) boundary conditions. At the wavelength of 1.55 µm, the confinement loss of the x-polarized mode is lower than 0.5 dB/km, whereas the loss of the y-polarized mode is larger than 50 dB/km. Compared with the case of x-polarized mode, the y-polarized mode can be suppressed in the PCF. Then, the SPSM operation is obtained. The proposed PCF can perform SPSM operation with broadband of 600 nm for considering the confinement loss ratio and the loss difference.

Tunable Single-Polarization Single-Mode Photonic Crystal Fiber Based on Liquid Infiltrating

We proposed and demonstrated a tunable single-polarization single-mode photonic crystal fiber (SPSM-PCF) based on selectively infiltrating liquid into air holes of high birefringence photonic crystal fiber (HB-PCF). A full-vector finite-element method (FEM) is used to analyze the SPSM operation range and its tunable characteristics. The starting wavelength of the SPSM operation range can be widely tuned from 2014 to 977 nm and the corresponding SPSM operation range can be tunable from 350 to 89 nm when the infiltrating index changes from 1.22 to 1.38. Experimentally, a tunable SPSM-PCF with a starting wavelength of SPSM operation range from 1591 to 1670 nm by increasing the temperature from 25°C to 65°C is realized. The tunable sensitivity is 1.975 nm/°C and the extinction ratio of the two orthogonal polarized modes is 17 dB.

一种四排短轴渐减椭圆空气孔阵列的单模单偏振光子晶体光纤

一种四排短轴渐减椭圆空气孔阵列的单模单偏振光子晶体光纤

Broadband Single-Polarization Single-Mode Operation in Highly Birefringent Photonic Crystal Fiber with a Depressed-Index Core

A novel design for a broadband single-polarization single-mode photonic crystal fibers is proposed and numerically analyzed by using a finite-element method. It is shown that the single-polarization single-mode operation spectral region of a highly birefringent photonic crystal fiber can be strongly enhanced by introducing a suitably down-doped silica rod inside the fiber core. In the proposed design, the single-polarization single-mode guidance can be realized in the wavelength range from 1.0 to 1.8 µm with the confinement loss less than 0.12 dB/km.

Design of a single-polarization single-mode photonic crystal fiber with a near-Gaussian mode field and wide bandwidth

Single-polarization single-mode (SPSM) fiber can efficiently eliminate polarization mode coupling, polarization mode dispersion, and polarization-dependent loss. Up to now, most single-polarization fibers have been designed based on form birefringence, which would result in a non-Gaussian field distribution and a small effective mode field area. In this paper, a novel structure of SPSM photonic crystal fibers based on the resonant coupling phenomena is proposed and analyzed by using a full-vector finite-element method with a second-order transparent boundary condition. From the numerical results it is confirmed that this fiber has a near-Gaussian mode field within the wavelength range from 1.46 to 2.2 μm, where only one polarized mode exists effectively, and the mode field area is about 79 μm(2) at the wavelength of 1.55 μm, matching that of the conventional single-mode fiber.

Single-polarization single-mode photonic crystal fiber based on index-matching coupling with a single silica material

We propose and analyze a novel design of single-polarization single-mode photonic crystal fiber based on index-matching coupling by using a finite-element method. The proposed fiber is designed such that there is a large differential loss between two polarizations of the fundamental mode by reducing two air holes in the cladding region which is composed of hexagonal structured air holes in pure silica. From the numerical analysis it is shown that single-polarization single-mode operation wavelength region can be tuned by adjusting the diameters of two defect air holes. In the proposed design, the spectral region over which the differential loss ratio is larger than 100 can be wider than 150 nm around the wavelength 1.55 or 1.31 μm. Another novel design that allows simultaneous single-polarization single-mode guidance in two wavelength windows centered at 1.55 and 1.31 μm is also proposed.

An asymmetric dual-core single-polarization single-mode photonic crystal fiber coupler

A vectorial finite element method (VFEM) is adopted to investigate the novel single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler which has asymmetric dual-core and two lines of enlarged air holes. It is demonstrated that the SPSM region of the designed fiber can be more than 250 nm wide with a set of optimized air-hole parameters and the width of the SPSM region could change slightly by fine adjustment of the inner large air holes. The coupling length between the odd and even x-polarization modes is also investigated through fine-tuning the large and small air-hole diameters.

Control of the fabrication parameters during the fabrication of photonic crystal fibers

The interplay between the fabrication parameters during the fabrication of photonic crystal fibers（PCF） are numerically analyzed. Relation between these parameters and the final fiber’s geometry is identified. With the cooperative control of drawing temperature and feed speed, the final hole structure can be effectively controlled by tuning the applied pressure. A single-mode PCF with its d/Λ approaching 0.45, and a PCF with high air-filling fraction, whose d/Λ equals 0.8, are successfully fabricated. For fabrication of PCFs with uneven-sized holes, parameter control alone is sometimes inadequate in achieving the desired geometry. Taking a single-polarization single-mode（SPSM） PCF structure as example, the preform’s geometry is redesigned for optimization by inverse calculation. And the required SPSM PCF can thus be fabricated.

Design of low-loss single-polarization single-mode photonic-crystal fiber based on polymer

A new structure for single-polarization single-mode photonic-crystal fiber is proposed and numerically analyzed by using a full vector finite element method with anisotropic perfectly matched layers. The cutoff wavelength of two linearly polarized states can be controlled artificially by varying the structure parameters of photonic crystal fiber. The confinement loss are also numerically calculated and optimized at 650 nm communication wavelength of polymer optical fiber. From the numerical results it is confirmed that the proposed fiber is low-loss single-polarization single-mode photonic-crystal fiber within the wavelength range from 0.63 to 0.73 µm, where only the slow-axis mode exists and the confinement loss is less than 0.05 dB m−1.

Characterization of single-polarization single-mode photonic crystal fiber using full-vectorial finite element method

A modal solution approach based on the powerful, finite element method (FEM) using a full-vectorial H-field formulation has been used to determine the single-mode operation of a photonic crystal fiber (PCF). The modal solution of the fundamental space-filling mode has also been obtained to identify the cutoff conditions of the waveguide modes. The FEM, with the perfectly matched layer boundary condition, has been developed and employed to characterize the leakage loss and the differential loss between the polarized modes of a PCF. The design approach for a single-polarization and single-mode PCF has also been discussed.

Design of a single-polarization single-mode photonic crystal fiber double-core coupler

A simple single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler with two cores is introduced. The full-vector finite-element method (FEM) is applied to analyze the modal interference phenomenon of the even and odd modes of two orthogonal polarizations and the power propagation within the two cores. Meanwhile, the SPSM coupling wavelength range and its corresponding coupling length for different structure parameters are numerically analyzed. The numerical results show that SPSM coupling can be realized with a broad range of wavelength, and the coupling length can be of millimeter magnitude. Moreover, the SPSM coupling wavelength range and the coupling length can be optimized by designing proper mirco-structure parameters of the coupler.

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.

Novel design for a single-polarization single-mode photonic crystal fiber at 1310nm

The paper reports a novel design for single-polarization single-mode (SPSM) operation at 1310 nm in photonic crystal fibers (PCFs), using a rectangular-lattice PCF with two lines of three central air holes enlarged. The proposed PCF, composed entirely of silica, is modeled by a full-vector finite-element method with anisotropic perfectly matched layers. Simulations show that wideband single-polarization operation can be easily realized with the proposed structure. This wideband SPSM operation, the low confinement losses, and the small effective mode area are the main advantages of the proposed fiber. The influence of varying PCF parameters on the SPSM operation is discussed, and numerical results show that the proposed fiber is a SPSM one with confinement loss less than 0.1 dB/km at wavelengths ranging from 1100 to 1460 nm and effective mode area about 4.3 μm 2 at 1310 nm.

Design of Wideband Single-Polarization Single-Mode Photonic Crystal Fiber

The present paper proposes a novel design for achieving single-polarization single-mode (SPSM) operation in photonic crystal fiber (PCF), using a rectangular-lattice PCF with two lines of three central air holes enlarged. The proposed PCF that is composed entirely of silica material is modeled by a full-vector finite element method with anisotropic perfectly matched layers. The position of the region of single polarization can be tuned freely by adjusting the size of the central enlarged air holes. Using this structure, an SPSM PCF with confinement loss less than 0.1 dB/km within the wavelength range from 1.20 to 1.66 mum and effective mode area about 5.9 mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 1.55 mum has been successfully designed. The proposed fiber is a nonlinear SPSM, which may be useful for nonlinear optical applications or applications with a wide SPSM operating bandwidth requirement

Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 /spl mu/m

Single-polarization single-mode (SPSM) operation of a highly birefringent (HB) photonic crystal fiber (PCF) is investigated in detail by using a full-vector finite-element method (FEM) with anisotropic perfectly matched layers (PMLs). The cutoff wavelengths of the two linearly polarized principal states can be designed by varying the structure parameters of the PCF. The confinement loss and splice loss to standard single-mode fiber for particular SPSM PCFs are calculated and optimized at both 1.30 and 1.55 /spl mu/m.

Numerical simulation of a novel rectangular-lattice single-polarization single-mode photonic crystal fiber

A novel structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed numerically based on a full-vector finite element method with anisotropic perfectly matched layers. Through optimization a fiber with confinement loss less than 0.1 dB/km in the wavelengths range of 1.38 to 1.61 μm is obtained. The corresponding design procedures for the novel SPSM-PCF are also presented.

Confinement losses and optimization in rectangular-lattice photonic-crystal fibers

Confinement losses in highly birefringent rectangular-lattice photonic-crystal fibers (RLPCFs) are investigated by the multipole method. The losses are strongly polarization dependent, which is due to the anisotropic properties of the cladding. The feature is applied to construct a new kind of single-polarization single-mode photonic-crystal fibers (PCFs), which is based on large differential loss between the two polarizations of the fundamental mode. Furthermore, it is found that the birefringence of RLPCFs is determined mainly by the air holes near the defect core. Consequently, a sandwiching (between triangular structures) rectangular configuration that has the property of reducing leakage loss while simultaneously retaining the birefringence of RLPCF is proposed.

Single-polarization single-mode photonic crystal fibers

A new structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed by using a full-vector finite element method with anisotropic perfectly matched layers. From the numerical results it is confirmed that the proposed fiber is low-loss SPSM-PCF within the wavelengths ranging from 1.48 to 1.6 μm, where only the slow-axis mode exists and the confinement loss is less than 0.1 dB/km.