High Birefringence Photonic Crystal Fiber Research Articles

A fourth-order Runge-Kutta in the interaction picture algorithm for simulating coupled generalized nonlinear Schrödinger equation and its error analysis

The numerical simulation method for accurately solving the coupled generalized nonlinear Schrödinger equations (C-GNLSE) is essential for describing the dynamic behavior of ultrashort pulse propagating in optical fiber and developing the corresponding nonlinear fiber-optic devices. C-GNLSE in the normal picture is first mapped into the interaction picture by the representation transformation, and then, the two coupled nonlinear partial differential equations in the interaction picture are solved in frequency domain, with synchronous data updating in each iteration step, by using the vector form of Hult’s fourth-order Runge-Kutta iterative scheme. The proposed vector form algorithm of fourth-order Runge-Kutta in interaction picture (V-JH-RK4IP) is verified by using it in simulating the supercontinuum generation in high birefringence photonic crystal fiber. Moreover, the V-JH-RK4IP algorithm also exhibits the highest accuracy and computational efficiency as compared to other classical algorithms.

Supercontinuum experimental study of V-type photonic crystal fiber with high birefringence

High nonlinear and high birefringent photonic crystal fiber is one of the most effective medium for supercontinuum generation, therefore we select the V-type photonic crystal fiber as the research object. Through the numerical simulation results of multipole theory, we determined that the V-type optical fiber has high birefringent and high nonlinear characteristics. Through experiments, we found that the birefringence of the fiber and the central wavelength of the incident light have great influence on the generation of supercontinuum: when the central wavelength of incident light in the anomalous dispersion region of the fiber, its spectrum is quite wide relatively, and the supercontinuum of the long axis is flat tar than that of the short exis and has more abundant spectral components; at the same wavelength of light, the polarization direction of the former is closer to 45°, the supercontinuum spectrum range is larger. With the increase of the incident pulse power, supercontinuum will spread wider, but will reach a saturation when the power is large enough.

Investigation of a new kind of high birefringence photonic crystal fiber

A kind of highly birefringent and highly nonlinear photonic crystal fiber (PCF) is proposed. The fundamental mode field, birefrin-gence, nonlinear coefficient, effective mode area and dispersion characteristic of the fiber are studied by the full-vector finite elementmethod. Simulation results show that the birefringence becomes larger by reducing the air hole pitch, and the birefringence reachesup to 10-2 at a wavelength of 1550 nm, which is about two orders of magnitude higher than that of the regular elliptic polarizationmaintaining fiber. At the same time, a nonlinear coefficient of 42 W-1·km-1 is obtained. There are two zero dispersion wavelengthsin the visible and the near-infrared region respectively, and flattened chromatic dispersion from 800 nm to 2000 nm is obtained. Sucha design provides a new approach to obtaining highly birefringent and highly nonlinear PCF, and the fiber has a broad prospect ofapplication in the polarization control, nonlinear optics and dispersion control.

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

Phenomenon in an alcohol not full-filled temperature sensor based on an optical fiber Sagnac interferometer

An alcohol not full-filled high-birefringence photonic crystal fiber (HiBi-PCF) temperature sensor based on an optical fiber Sagnac interferometer (OFSI) is demonstrated and investigated in detail. A new phenomenon that the resonant dip wavelengths of the temperature sensor blueshift with temperature increasing is observed, which is contrary to that of the previously reported alcohol filled HiBi-PCF OFSI temperature sensor. By considering the influences of the group birefringence and the thermo expansion of alcohol, this phenomenon is explained very well. The temperature sensitivity of the proposed sensor is about -1.17 nm/°C and is only one-sixth of that of the alcohol full-filled HiBi-PCF OSFI.

Investigation of high birefringence and negative dispersion photonic crystal fiber with hybrid crystal lattice

Aiming at the requirements of high birefringence and negative dispersion in fiber-optic communication and sensing systems, a novel type of photonic crystal fiber (PCF) is proposed. In this structure, rectangular holes are arranged as hybrid lattice in the core and two bigger air holes symmetrical in the first cladding layer are added to gain high birefringence. Simulation results show that this kind of PCF exhibits high birefringence with a level of 10−2, which will obtain better polarization. The negative dispersion is obtained over a wide wavelength range simultaneously, which has important applications in designing of dispersion compensation fibers.

Polarization splitting filter characteristics of Au-filled high-birefringence photonic crystal fiber

Polarization splitting wavelength-selective characteristics of Au-filled high-birefringence photonic crystal fiber (HB-PCF) based on the finite element method is investigated. Numerical results show that the polarization splitting effect can be observed in metal-filled HB-PCF. The resonances points and strength in two polarizations can be adjusted by changing the fiber birefringence, the pitch between the adjacent air holes and the size of the metal wires. Finally, two kinds of Au-filled HB-PCFs with completely polarization splitting and filtering characteristics in communication wavelength are designed. Results show that this polarization splitting effect in metal-filled HB-PCF is very useful for further studies in polarization-dependent wavelength-selective applications and other fiber-based plasmonic devices.

Wavelength-selective characteristics of high birefringence photonic crystal fiber with Au nanowires selectively filled in the cladding air holes

Filter characteristics of a designed gold-filled high birefringence photonic crystal fiber are investigated based on the finite element method. The wavelength filter resonances in the high birefringence photonic crystal fiber occur at different points for different polarized directions, and the resonance strength in the x-polarized case is much weaker than that in the y-polarized case. The much more obvious splitting filter characteristics and different resonance strength imply the study and application values in splitting and single polarization fiber devices. The simulation results show that increasing the number of the gold wires only enhances the resonance strength when there is no surface plasmon supermode formed. With the diameters of the gold wires increasing, the response wavelength moves to a longer wavelength, and the strength becomes stronger. When the diameter is increased to 1.4 μm, the response wavelength in the x-polarized case can be tuned to 1.318 μm, which is the communication wavelength. The strongest resonance occurs at 1.2375 μm in the y-polarized case, and the peaking loss can reach 435.83 dB/cm.

Numerical analysis of a novel high birefringence photonic crystal fiber

In order to confine mode field energy effectively and obtain high birefringence, a new type of photonic crystal fiber (PCF) is proposed, which consists of air cores arrayed with pentagonal core and hexagonal cladding. Investigations show that high birefringence can be obtained by changing the aperture of the two symmetry holes outside the core. Simulation results show that the birefringence of this PCF reaches the magnitude of 10−3 which fulfills the requirements of high precision applications in optical systems. In addition, nonlinear coefficient reaches the magnitude of 103km−1w−1 after optimization, which will find application in nonlinear optics.

Widely Wavelength-Tunable Two-Colored Solitons and Small Spectral Component for Broadband Mid-Infrared Wavelength Generation in a Highly Birefringent Photonic Crystal Fiber

With a highly birefringent photonic crystal fiber (HB-PCF) specially designed and fabricated in our laboratory, the two-colored solitons and small spectral component formed by the balance between the dispersion and birefringence effect are generated above 2000 nm when the polarization direction of pump pulse is aligned along the fast and slow axis of HB-PCF. When the average power of the pump at 870 nm increases from 100 to 300 mW, the broadband solitons at the fast and slow axis and small spectral component can be efficiently generated from 2120 to 2230 nm, 2070 to 2180 nm, and 2260 to 2370 nm, and the tunable wavelength range can be up to 300 nm. To the best of our knowledge, the largest span of soliton wavelength shift over 1300 nm is achieved. The widely tunable soliton pulse and small spectral component can provide the particularly useful short-pulse source for the mid-infrared photonics and spectroscopy.

Strain Effect on Differential Phase Sensitivity in Two-Mode Fibers

The modular differential phase characteristics of elliptical core fiber (ECF) and high- birefringence photonic crystal fiber (HB-PCF) are presented. The results show that HB-PCF has a larger range of wavelengths for two-mode operating than ECF. And when the longitudinal strain is applied on the fiber, the modular propagation constant difference between and modes is the most important factor for differential phase sensitivity. With the wavelength increases, the differential phase sensitivity of ECF decreases whereas that of HB-PCF changes in opposite way. And HB-PCF is more sensitive to strain than ECF.

Characteristics Analysis of High Birefringence Photonic Crystal Fiber with Pentagonal Air-Core

A new type of photonic crystal fiber (PCF) with pentagonal air-core is proposed, which consists of octagonal air holes in the cladding. In addition, five elliptical air holes are embedded in the inner layer to enhance the birefringence characteristic. Characteristics of this PCF are analyzed by using of Finite Element Method (FEM). Numerical results show that this kind of PCF exhibits high birefringence with the level of 0.001 after optimization, which will find application in optical sensing systems.

Characteristics Analysis of High Birefringence Photonic Crystal Fiber with Pentagonal Air-Core

A new type of photonic crystal fiber (PCF) with pentagonal air-core is proposed, which consists of octagonal air holes in the cladding. In addition, five elliptical air holes are embedded in the inner layer to enhance the birefringence characteristic. Characteristics of this PCF are analyzed by using of Finite Element Method (FEM). Numerical results show that this kind of PCF exhibits high birefringence with the level of 0.001 after optimization, which will find application in optical sensing systems.

Magnetic Field Measurements Based on Terfenol Coated Photonic Crystal Fibers

A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT) over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field.

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.

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.

Design of high birefringence and low confinement loss photonic crystal fibers with five rings hexagonal and octagonal symmetry air-holes in fiber cladding

We present a new cladding design for high birefringence and low confinement loss photonic crystal fibers (PCFs) using a full-vector finite element method with anisotropic perfectly matched boundary layer. Six cases of PCFs are proposed for comparison. The proposed cladding in PCFs is composed of five rings of air-holes. Air-holes on the inner two rings are arranged in a hexagonal symmetry whereas, air-holes on the outer three rings are arranged in an octagonal symmetry in fused silica. Results show that suitable design air-holes on the inner two rings will significantly increase the birefringence, whereas, elliptical holes with major axis along x-axis on the outer three rings will provide strong confinement ability. The highest modal birefringence and lowest confinement loss of our proposed case five structure at the excitation wavelength of λ = 1550 nm can be achieved at a magnitude of 0.87 × 10−2 and less than 0.01 dB/km with only five rings of air-holes in fiber cladding.

High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror

A compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled high-birefringence photonic crystal fiber (PCF) is proposed and experimentally demonstrated. The output of the FLM is an interference spectrum with many resonant dips, of which the wavelengths are quite sensitive to the change of the refractive index of the filled alcohol for the interference of the FLM. Simulation analysis predicts a high temperature sensitivity, and experimental results show it reaches up to 6.6 nm/°C for the 6.1-cm-long PCF used in the FLM.

Tunable single- and dual-wavelength erbium-doped fiber laser based on Sagnac filter with a high-birefringence photonic crystal fiber

In this paper, we observed and experimentally investigated a high-performance single- and dual-wavelength erbium-doped fiber ring laser based on a Sagnac filter which contains a section of high-birefringence photonic crystal fiber (HB-PCF) and a polarization controller. Incorporation of the high-birefringence photonic crystal fiber can suppress multimode oscillation, improve power stability and increase the optical signal-to-noise ratio (SNR). Wavelength tunable was achieved by using a polarization controller in the Sagnac filter. Highly stable single-, dual-wavelength oscillations are tunable within a wavelength range from 1550 to 1562 nm and SNR as high as 57 dB with narrow line width about 0.011 nm, is experimentally demonstrated.

Improved high birefringence photonic crystal fibres with dispersion flattened and single mode operation

A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results show that the improved PCF possesses the properties of a flat dispersion and single mode operation. Moreover, with the operating wavelength λ = 1.55 μm, the modal birefringence increases greatly in comparison with that of the original PCF, and the leakage loss is about 104 times smaller than that of the original PCF because the modification gives rise to the strong confinement of guided modes. It is expected that the improved PCF can be used as high birefringence and dispersion flattened fibres.