Dual-core Photonic Crystal Fiber Coupler Research Articles

Saturable absorber based on the broadband composite-liquid-filled dual-core photonic crystal fiber coupler

A dual-core photonic crystal fiber coupler based on the heavily G e O 2 -doped-silica-air cladding and composite-liquid ( C S 2 and C 2 C l 4 ) core is proposed to obtain the saturable absorber (SA). It is demonstrated by numerical simulations that the SA with appropriate parameters can exhibit the normal dispersion, high nonlinearity, and flat profile of the linear coupling lengths in the wavelength range from 1500 to 2000 nm. The input pulses with durations > --> 2 p s exhibit relatively high transmissions and low saturable powers mainly because of the strong effect of stimulated Raman scattering in the SA. Consequently, the SA with the G e O 2 concentration ratio of 80 mol% can be employed in both the erbium- and thulium-doped fiber mode-locked lasers with all-normal or large net-normal dispersion. The dissipative soliton pulses with tunable wavelengths can be obtained in both cases.

Bending dual-core photonic crystal fiber coupler

In this paper, we systematically study a designed structure of a bending dual-core photonic crystal fiber (PCF). We propose the controllable wavelength-selective coupling PCF. This coupler allows highly accurate control of the filtering wavelength. The different wavelengths can be selected by controlling the bending radius of the fiber. Coupling characteristics of novel bending wavelength-selective coupling PCF are evaluated by using a vector finite element method and their application to a multiplexer demultiplexer (MUX–DEMUX) based on the novel coupler is investigated. When the fiber length is 4168μm, the bending radius of PCF couplers for 1.48/1.55μm, 1.3/1.55μm, 0.98/1.55μm, and 0.85/1.55μm is calculated, respectively, and the beam propagation analysis is performed. Different from the traditional wavelength-selective coupling PCF, the dual-core PCF is bent and it can realize the separation of multiple wavelengths.

Design and optimization of a novel broadband and polarization-insensitive dual-core photonic crystal fiber coupler over the whole optical communication band

In this paper, a novel broadband polarization-insensitive dual-core photonic crystal fiber with elliptical central hole is proposed and the influence of its structural parameters on coupling characteristic is investigated in detail by the full-vector finite element method. Through optimizing the fiber structural parameters, broadband and polarization-insensitive characteristics are achieved over the whole optical communication band from 1.225 m to 1.675 m. The variation of coupling ratio is stabilized at 50% 1%, and the coupling ratio difference between x polarization and y polarization is less than 0.5% overall the wavelength range. Due to its relatively independent of cores and elliptical central hole and suitable structural parameters, this fiber meets the application requirements, that is, easy to fabricate, easy to splice and low splice loss. This research is freed from the current coupler limit: narrow bandwidth, wavelength dependence, polarization-sensitive, difficulty of fabricating, thereby provides the theoretical basis for the study of the large capacity high speed all-optical networks and multi-wavelength tunable fiber laser.

Design and optimization of broadband and polarization-insensitive dual-core photonic crystal fiber coupler

In this paper, we propose a novel (to our knowledge) broadband and polarization-insensitive dual-core photonic crystal fiber (PCF) coupler through the introduction of an elliptical-shaped central air hole to offset the slight birefringence arising from the dual core. With a full vectorial finite element method and anisotropic perfectly matched layers as the external boundaries, the impact of several fiber parameters on the coupling characteristics of dual-core PCF is investigated in detail. Through optimizing the main fiber parameters, including core diameter, size and ellipticity of the central air hole, and refractive index difference, broadband and polarization-insensitive characteristics are achieved in the wavelength range from 0.8 to 1.7 μm. The variation of the coupling ratio is stabilized at 50±1%, and the coupling ratio difference between x polarization and y polarization is less than 2% over the wavelength range. This dual-core PCF makes it easier to develop a 3 dB coupler over a wide wavelength for passive optical networks and large optical systems.

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By means of numerical simulation analysis of asymmetric dual-core photonic crystal fiber coupler,it is shown that this kind of coupler can neglect the effect of polarization property due to approximate coupling strength of two different coupling modes in two different polarization directions.Meanwhile,at a certain splitting ratio,the coupler with different wavelength response can produce wideband dual-core coupler with different splitting ratio,and the properties such as bandwidth,splitting ratio inaccuracy,coupling length can be greatly improved compared to the usual wideband fiber coupler.It can provide theoretical support for designing wideband asymmetric dual-core photonic crystal fiber coupler.

Nonlinear vortex modes in dual-core photonic crystal fiber couplers

We study the different families of vortex-type modes that can exist in a photonic crystal fiber with two close defects forming a dual-core coupler and presenting the Kerr nonlinearity. Those complex modes bifurcate from the real double-dipole states leading to different states with different phase structures. When power is high enough, single- and double-vortex modes as well as combinations of vortex and fundamental modes arise. Also, families of discrete vortices formed by multipoles located inside the cores are found. We classify the different families, describe their nontrivial bifurcations, and study the stability of the states identifying different scenarios.

The impact of elliptical deformations for optimizing the performance of dual-core fluorine-doped photonic crystal fiber couplers

In this paper we study the impact of elliptically-deformed features such as cladding air-holes and elliptically-modulated cores, as ingredients for optimizing the coupling characteristics of dual-core fluorine-doped photonic crystal fiber (PCF) couplers. We provide a detailed numerical investigation by using a trial and error approach for optimizing the propagation characteristics of fluorine-doped PCF couplers. Typical characteristics of the newly proposed PCF coupler structure are: wavelength-flattened coupling characteristics between 0.7 mum and 1.6 mum wavelength range, coupling efficiency of 50+/-1 % from 0.9 mum to 1.6 mum, and a reasonably small coupling length of 1.3 cm. In addition we have elaborately derived the design parameters so that our proposed dual-core PCF coupler exhibits polarization-insensitive characteristics verified by using a full-vectorial beam propagation method. The proposed dual-core PCF can be effectively used as a 3-dB coupler, over a wide wavelength range.

Nonlinear dual-core photonic crystal fiber couplers

We study nonlinear modes of dual-core photonic crystal fiber couplers made of a material with the focusing Kerr nonlinearity. We find numerically the profiles of symmetric, antisymmetric, and asymmetric nonlinear modes and analyze all-optical switching generated by the instability of the symmetric mode. We also describe elliptic spatial solitons controlled by the waveguide boundaries.

Modeling of a highly nonlinear chalcogenide dual-core photonic crystal fiber coupler

The switching operation of a nonlinear dual-core photonic crystal fiber (PCF) coupler, based on a highly nonlinear As2Se3 chalcogenide glass, is numerically studied for the first time. Combining the standard coupled-mode formulation with a full-vectorial integral equation analysis of the PCF geometry, we show that the device parameters can be tailored to achieve switching power requirement ∼1 W at a coupler length of only few centimeters. The dispersion results show that efficient switching can be attained for pulsewidths greater than ∼2 ps.

Coupling characteristics of dual-core photonic crystal fiber couplers

Coupling characteristics of dual-core photonic crystal fiber (PCF) couplers are evaluated by using a vector finite element method and their application to a multiplexer-demultiplexer (MUX-DEMUX) based on PCF is investigated. The PCF couplers for 1.48/1.55-m, 1.3/1.55-m, 0.98/1.55-m, and 0.85/1.55-m wavelength MUX-DEMUX are designed and the beam propagation analysis of the proposed PCF couplers is performed. It is shown from numerical results that it is possible to realize significantly shorter MUX-DEMUX PCFs, compared to conventional optical fiber couplers.