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.

All-fiber circular polarization beam splitter based on helically twisted twin-core photonic crystal fiber coupler

Abstract In this work it is proposed a novel all-fiber circular polarization beam splitter (CPBS). The design is based on helically twisted twin-core photonic crystal fiber coupler (HTTC-PCF). The main characteristic of the proposed CPBS device is the capacity to spatially split circularly polarized optical modes with opposite handedness at the twin-cores. For the CPBS to work, a single arbitrary rotated linearly polarized optical mode can be used as an input signal as well as a combination of two circularly polarized modes with opposite handedness. The coupling characteristics of HTTC-PCF were analyzed as function of the photonic crystal fiber (PCF) structural parameters, helical twist-rate, wavelength and temperature. The analyses were performed using a full vector finite element method with helical space mapping formalism and the supermode theory. An all-fiber CPBS with 24.76 mm length, extinction ratio ( ER ) of ~50 dB and spectral bandwidth of ~36.79 nm (for ER > 10 dB) and ~ 11.43 nm (for ER > 20 dB) was obtained at 1550 nm central wavelength for a twist-rate of 15.70 rad/mm.

Nonlinearity effect on dual photonic crystal fiber coupler for generating fully optical logic gates

AbstractIn this work, we present a numerical investigation of the asymmetric double nonlinear coupling of photonic crystal fibers in an on‐off switch to obtain fully optical logic gates. Ultra‐short pulses (100 fs) are propagated through the device in three distinct excitation power regimes, power below critical (Po = 72 kW, where Po represents the excitation power of the device), critical power (Pc = 103.5 kW, where Pc represents critical Power for which the power switching is 50% for both guides. There are cases where Po is above the critical value, there are cases that is below), and power above critical (Po = 110 kW). The pulse switching characteristics are analyzed as a function of the input power and the nonlinearity profile (β‐beta) inserted in one of the component guides. The nonlinearity profiles follow the regimes: constant, increasing and decreasing, and high order effects, such as third‐order dispersion, intrapulse Raman scattering and self‐steepening are included in the generalized Schrödinger nonlinear equation governs the pulse propagation dynamics. The results show that the proposed device can be used to obtain AND, OR, and NOT logic gate. Numerical studies were done from the coupled‐coupled equations solved using the fourth‐order Runge‐Kutta method, using MATLAB as a programming tool for solving equations. The implementation of fully optical logic gates tends to revolutionize new digital systems in the field of data storage, such as optical memory, “replacement” of electronic circuits among other applications. Optical systems have a great advantage as they are free from electromagnetic interference and have high rates of data transmission.

Small coupling length with a low confinement loss dual-core liquid infiltrated photonic crystal fiber coupler

In this paper, a dual-core liquid filled photonic crystal fiber coupler (PCFC) with rectangular (RPCFC) and hexagonal (HPCFC) geometry is presented from the 1200 to 1800 nm wavelength range. In the proposed design, super flint (SF10) glass is used as the background material and water, chloroform, and benzene are infiltrated in the dual-core, independently. The properties of the guided modes are studied by the finite difference time domain (FDTD) method with a perfectly matched layer (PML) boundary condition. Results reveal very small confinement loss with a low coupling length and birefringence for the wide wavelength range. At the 1.55 μm wavelength, RPCFC shows 0.000318, 0.000358, and 0.000379 m coupling lengths for the water, chloroform, and benzene filled dual-core, respectively. Additionally, the confinement loss of 1.57×10−7, 1.22×10−7, and 1.05×10−7 db/km is achieved through RPCFC. Moreover, both the PCFCs present a small polarization variation. Therefore, the proposed PCFC models can be used in optical communication systems, and polarization-independent and high temperature-sensitive applications areas.

Optimization of Photonic Crystal Polarization Handling Devices Using Trust Region Algorithms

In this paper, the trust region optimization techniques are used for the design of photonic crystal polarization handling devices. The trust region algorithms are based on quadratic surrogate models with no derivative requirements to replace the objective function in the optimization process. A new box constrained trust region algorithm is employed for the first time to the best of our knowledge along with full vectorial finite difference methods to optimize a passive polarization rotator (PR) based on silica photonic crystal fiber (PCF). The reported PCF PR has a device length of 204 μm with nearly 100% polarization conversion ratio at operating wavelength λ of 1.55 μm. Further, an unconstrained trust region (UTR) algorithm is used for optimizing the coupling characteristics of a soft glass nematic liquid crystal (NLC) PCF coupler. The optimized coupler can separate the two polarized beams with compact length of 380 μm and low crosstalk at λ = 1.55 μm. Furthermore, a polarization independent NLC-PCF multiplexer–demultiplexer is proposed for wavelengths of 1.3 and 1.55 μm using the UTR technique with a compact device length of 475 μm and low crosstalk for the two polarization states.

Optimization of polishing parameters for optical coupler based on side-polished photonic crystal fiber

The rapid development in areas such as fiber-optic communication, fiber lasers, and high power transmission has generated an increasing demand for photonic crystal fiber (PCF). However, there is no well-proven approach for PCF coupler fabrication because most approaches proposed introduce defects that are non-negligible in practice. Previously, we have made an attempt by applying side-adhering technique to PCF coupler fabrication. This paper presents our recent effort in establishing a model of side-polished PCF (SPPCF) coupler and tuning various fabrication parameters in search for its desirable characteristics. It is found that the optimal coupling effect is achieved when the residual radius is set 5.7 μm and the polishing angle is set 0°. The optimizations presented in this paper may serve as a foundation for further research and development of SPPCF coupler.

Design of a dual-core liquid-filled photonic crystal fiber coupler and analysis of its optical characteristics

The photonic crystal fiber coupler (PCFC) is one of the peculiar devices that play a major role in the future of optical networks. Dual-core PCFCs have many advantages over the conventional optical couplers such as more flexible design and shorter coupling length. In this paper we propose a silica-based PCFC with a hexagonal lattice structure, and important properties such as dispersion, effective refractive index, propagation characteristics, and coupling length are analyzed in comparison with benzene and chloroform liquid-filled PCFCs. The above properties are investigated under different geometrical parameters such as hole-to-hole spacing and different air hole diameter within a wide range of wavelengths. By proper adjustment of the dual-core PCFCs, the coupling lengths of 0.0006, 0.007, and 0.0008 m are achieved in the silica-, benzene-, and chloroform-filled PCFCs, respectively. Likewise, the dispersion values of −6987, −7055, and −6684 ps/(nm km) and the propagation constants of 10.9, 11.08, and 10.6 (×106) rad/m are achieved in silica-, benzene-, and chloroform-filled PCFCs, respectively.

Design of single-polarization single-mode coupler based on dual-core photonic crystal fiber

A single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler is designed and inves- tigated by using full-vector finite-element method with the anisotropic perfectly matched layer. We numerically analyze the SPSM coupling properties with respect to the structure parameters and confinement loss character- istics. The results reveal that the coupling length between dual cores is as small as millimeter order of magnitude due to the wide silica bridge of energy transfer, and the SPSM coupling region can be tailored to cover the communication windows of 1.3 or 1.55 μm with optimized design parameters. Moreover, the confinement loss of x polarization is 3 orders of magnitude larger than that of y polarization in single polarization range. The proposed SPSM PCF coupler may find application in polarization-sensitive systems. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution

Ultra‐compact liquid crystal dual core photonic crystal fibre multiplexer–demultiplexer

In this study, the authors propose a novel design of ultra-compact multiplexer–demultiplexer (MUX–DEMUX) based on silica photonic crystal fibre coupler. The suggested design has two large holes infiltrated with nematic liquid crystal of type E7. The reported MUX–DEMUX has short device length of 436 µm with low crosstalk better than −20 dB with bandwidths of 35 and 10 nm around operating wavelength of 1.3 and 1.55 μm, respectively. The simulation results are obtained using full-vectorial finite-difference method together with full-vectorial beam propagation method.

A projection operator approach for computing the dynamics of AS2S3 chalcogenide birefringent photonic crystal fiber coupler

A variety of AS2S3 chalcogenide photonic crystal fiber coupler of special properties are proposed to study the role of birefringence in all optical coupling characteristics based on the projection operator method (POM). The equations of motion describing the dynamics of the individual pulse parameters through x- and y-polarized modes are arrived at by employing POM from the coupled nonlinear Schrödinger equations. From the pulse parameter dynamics, it is observed that the amplitudes of the polarization components are significantly influenced by the pulse being introduced with different polarizing angle even at low input power level. Such a selective polarizing angles of the input pulse will provide efficient control over the desired splitting ratio as well as the ability to decide the desired polarization component.

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.

Research on Coupler of Single Mode Fiber with Photonic Crystal Fiber

A coupler of single mode fiber with photonic crystal fiber with a coupling ratio of 0 to 90% was fabricated with a new method called Auto-deposition Fused Side-adhere. A model for coupler of side-polished single mode fiber with side-polished photonic crystal fiber was established which proves it feasible to make such a coupler practically. In the range of 1520~1620nm, the Wavelength Dependent Loss (WDL) of the through port was 0.3dB and of the coupled port was 5dB. The Polarization Dependent Loss of through port was 0.25dB and 0.31dB at 1310nm and 1550nm, and the WDL of coupled port was 1.46dB and 1.75dB. When temperature changed from 10°C to 80°C and humidity changed from 10% to 70%, coupling ratio changed about 7% to 16%. It can be concluded that a steady coupler of single mode fiber with photonic crystal fiber can be made with the Auto-deposition Fused Side-adhere Coupling method, which can give a reference method and lay an experimental foundation for the fabrication of photonic crystal fiber coupler.

Triple-core collinear and noncollinear plasmonic photonic crystal fiber couplers

Numerical analysis of single and multiple gold nanowires embedded in triple cores arranged in collinear and noncollinear configurations in photonic crystal fibers (PCFs) is reported. A full-vectorial finite element method is used to achieve coupling characteristics of plasmonic PCF couplers for both x and y polarizations. It is demonstrated numerically that the PCF plasmonic couplers exhibit polarization-independent tunable broadband filter characteristics that can be tuned according to the diameter of the embedded gold rod(s).

Research of Numerical Simulation for Multi-Core Photonic Crystal Fiber Couplers

In this paper, multi-core photonic crystal fiber couplers are characterized and numerically simulated with Mangan et als theory and beam propagation method. We propose a kind of 1×3 multi-core photonic crystal fiber couplers with broadband characteristics and the identical split ratio within the range from 1300nm to 1800nm. If the proper length of the couplers is chosen, light couple intensity is completely the same by periphery there-core fiber with broadband characteristics. It provides a theoretical basis for the practice of multi-core photonic crystal fiber couplers.

Power dependent pulse delay with asymmetric dual-core hybrid photonic crystal fiber coupler

Abstract We propose a novel asymmetric dual-core hybrid photonic crystal fiber (PCF) coupler composed of a silicon tube as the left core and a silica core as the right core. The control of picosecond pulse delay is achievable by means of power adjusting. The transmission modes, dispersion characteristics and coupling coefficients of the proposed coupler are investigated numerically. The results demonstrate that it is possible to obtain 2.0 ps time delay for soliton pulse with 2.0 ps temporal width within 1 cm length. Further numerical results show that the coupler can generate 10.0 ps undistorted time advance within 5 cm length.

All-Optical Steering of Light Through Nonlinear Twin-Core Photonic Crystal Fiber Coupler at 850 nm

We intent to investigate the dynamics and steering characteristics of an optical pulse propagation through photonic crystal fiber coupler (PCFC) using the projection operator method (POM) at 850 nm. For the proposed study, we begin with the analysis of silica PCFC design. From the proposed design, we examine the propagation of Gaussian pulse through PCFC, by means of coupled nonlinear Schrodinger equations. By employing POM, we derive the equations of motion describing the dynamics of the pulse parameters, called collective variables (CVs), namely the amplitude, pulse width, phase and chirp. The corresponding results obtained through POM are compared and verified numerically by split step Fourier method (SSFM). Furthermore, we propose a novel chloroform filled PCF structure that operates as a single mode at 850 nm, featuring an enhanced dispersion and nonlinearity for efficient switching, thus enabling to accomplish switching at a low input pulse power and low loss over shorter distances. Efficient optical pulse switching through both the designs are demonstrated through the simulation of the transmission curve. From the transmission curve, we infer that efficient switching can be achieved at relatively low input power in the proposed chloroform filled PCF.

Numerical Analysis of Coupling Characteristics of Tunable Photonic Crystal Fiber Coupler for Nonlinear Optical Microscopy

As a kind of significant fiber device, an optical fiber coupler can make the nonlinear optical microscopy more compact and flexible for in vivo imaging. We numerically investigate the coupling efficiencies of side-polished large mode area endlessly single mode photonic crystal fiber coupler over the visible and near infrared wavelength range by using improved fully vectorial effective index method and weak-coupling theory. We find that appropriate combinations of the core distance and the angle between two side-polished fibers can accomplish a large mode area endlessly single mode photonic crystal fiber coupler to simultaneously deliver the near infrared laser for excitation and split the fluorescence for detection.

Fabrication of Polarization-Maintaining Photonic Crystal Fiber Coupler with Air Hole State Control Using CO<sub>2</sub> Laser Irradiation Technique

Fabrication of Polarization-Maintaining Photonic Crystal Fiber Coupler with Air Hole State Control Using CO<sub>2</sub> Laser Irradiation Technique

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 analysis of a low-loss terahertz directional coupler based on three-core photonic crystal fibre configuration

A novel kind of terahertz directional optical fibre coupler is proposed. The coupling characteristics and operation bandwidth of the three-core photonic crystal fibre coupler are investigated. Numerical results show that it is possible to achieve a broadband terahertz fibre coupler with a small fibre length of a few centimetres. In addition, a modified configuration, which can achieve a wider bandwidth and lower absorption loss, is proposed.