Birefringent Photonic Crystal Fiber Research Articles

Extremely high birefringent slotted core umbrella-shaped photonic crystal fiber in terahertz regime

Extremely high birefringent slotted core umbrella-shaped photonic crystal fiber in terahertz regime

Coupled-generalized nonlinear Schrödinger equations solved by adaptive step-size methods in interaction picture

We extend two adaptive step-size methods for solving two-dimensional or multi-dimensional generalized nonlinear Schrödinger equation (GNLSE): one is the conservation quantity error adaptive step-control method (RK4IP-CQE), and the other is the local error adaptive step-control method (RK4IP-LEM). The methods are developed in the vector form of fourth-order Runge–Kutta iterative scheme in the interaction picture by converting a vector equation in frequency domain. By simulating the supercontinuum generated from the high birefringence photonic crystal fiber, the calculation accuracies and the efficiencies of the two adaptive step-size methods are discussed. The simulation results show that the two methods have the same global average error, while RK4IP-LEM spends more time than RK4IP-CQE. The decrease of huge calculation time is due to the differences in the convergences of the relative photon number error and the approximated local error between these two adaptive step-size algorithms.

Temperature-insensitive polarimetric vibration sensor.

Vibration measurement is a frequent measurement requirement in a number of areas. Optical vibration sensors have many advantages over electrical counterparts. A common approach is to optically detect the vibration induced mechanical movement of a cantilever. Nevertheless, their practical applications are hindered by the cross-sensitivity of temperature and dynamic instability of the mechanical structure, which lead to unreliable vibration measurements. Here, we demonstrate a temperature insensitive vibration sensor that involves an enclosed suspended cantilever integrated with a readout fiber, providing in-line measurement of vibration. The cantilever is fabricated from a highly birefringent photonic crystal fiber by chemical etching and fused to a single-polarization fiber. Mechanical vibration induced periodic bending of the cantilever can significantly modify the state of polarization of the light that propagates along the photonic crystal fiber. The single-polarization fiber finally converts the state of polarization fluctuation into the change of output optical power. Therefore, the vibration could be demodulated by monitoring the output power of the proposed structure. Due to the special design of the structure, the polarization fluctuation induced by a variation of the ambient temperature can be significantly suppressed. The sensor has a linear response over the frequency range of 5 Hz to 5 kHz with a maximum signal-to-noise ratio of 60 dB and is nearly temperature independent.

Design of broadband and compact mid-infrared polarization beam splitter based on all-circular air holes with low loss

A mid-infrared (mid-IR) broadband polarization beam splitter (PBS) based on a gallium sulfide dual core highly birefringent photonic crystal fiber is proposed. The high birefringence and dual core are achieved by introducing two kinds of circular air holes with different diameters into the fiber core. The mode coupling characteristics of the even and odd modes in the proposed dual core PBS are investigated using the finite-difference time-domain method and coupled-mode theory. The numerical simulation results indicate that, when the incident light frequency is 4.5 μm and the PBS length is 277.1 μm, a wide bandwidth of 170 nm (from 4.472 to 6.642 μm) with a polarization extinction ratio (ER) >20 dB is obtained in the mid-IR waveband. The highest ER of 112.8 dB is realized. The designed PBS will find potential applications in mid-IR optical sensing, communication, and imaging systems because of its wide bandwidth and ultrashort length.

Polished photonic crystal fiber refractive index sensor based on surface plasmon resonance

A polished photonic crystal fiber sensor based on surface plasmon resonance for refractive index (RI) detection is proposed and analyzed by finite element analysis. The design of polishing can greatly increase the birefringence of photonic crystal fiber and ensure a uniform coating film, thus improving sensor performance. The outer air of the structure is arranged in half of an octagonal shape, and the inner layer is arranged in a quadrilateral shape, which can effectively improve coupling strength in the y -polarization direction. The sensor works mainly in visible and infrared wavelengths with a detection range of 1.33 to 1.38. Through analysis of external RI changes, pore structure parameters, and silver mold thickness, the maximum sensitivity is 14800 nm/RIU, maximum amplitude sensitivity is 766.7008 R I U − 1 , resolution is up to 6.7568 × 10 − 6 R I U , and maximum figure of merit is 548.1481. The sensor is suitable for biomedicine, environmental monitoring, chemistry, and other fields.

A large birefringence and high nonlinearity liquid crystal photonic crystal fiber with low confinement loss

Through filling the liquid crystal E7 into the defect position of the photonic crystal fiber (PCF) which possesses full circular air hole structure, a PCF with adjustable optical performance is designed. The effect of external temperature and magnetic field on its optical properties is analyzed by adopting the finite element method. The results reveal that its confinement loss is reduced, and the dispersion performance is also improved. Besides, the high birefringence bandwidth can covers all the S, C, L and U communication bands and the it reaches to the order of 10−1 at the wavelength of 1.55 μm; a high nonlinear coefficients (about 3 × 105 W−1km−1 and 9 × 105 W−1km−1 in X, Y polarization directions respectively) are also obtained. Most importantly, the optical performance can be adjusted without changing its structural parameters. It provides a new method for obtaining PCFs with good optical performance, and it has potential applications in the fields of polarization control, dispersion management, super-continuum generation and optical fiber sensing.

An ultra-high birefringent and nonlinear decahedron photonic crystal fiber employing molybdenum disulphide (MoS2): A numerical analysis

A novel Decahedron photonic crystal fiber (DHn-PCF) is proposed. To sustain high birefringence and nonlinearity, the central elliptical core is filled with a highly nonlinear 2D material molybdenum disulphide (MoS2). The significant performance parameters of the proposed DHn-PCF like birefringence, nonlinearity, confinement loss, and core power fraction has been investigated with change in its structural parameters. Simulation results confirmed an exceptionally high birefringence and nonlinearity of 0.632 and 9.68 × 105 W−1 Km−1 with the outstanding core power fraction of 98.6% for the well-known communication window at 1.55μm. Besides, the effective material loss (EML) and confinement loss (CL) are also found very low as 0.0302cm-1 and 8.7×10-10dB/mfor the same communication window. Therefore, with all these excellent outcomes, the proposed DHn-PCF proves itself a potential candidate for polarization maintenance, residual polarization compensation, dispersion compensator, bio-medical imaging, supercontinuum and solitons generation, high bit data rate telecommunication and sensing application.

A highly birefringent photonic crystal fiber with compact cladding layers suitable for fiber optic gyroscope application

A size reduced cladding layer of highly Birefringent photonic crystal fiber (PCF) that is suitable for fiber optic gyroscope application is proposed in this paper. A pair of minimized and enlarged air holes in the innermost layer of PCF is responsible for high birefringence and enlarged outer layer air holes are responsible for low confinement loss. The optimized geometrical parameters for this novel PCF are chosen so as to ensure high birefringence and low confinement loss. Fabrication of this proposed PCF is simplified by reducing the cladding layers. Obtained birefringence of this PCF is about 6.1 × 10−4 and the confinement loss is about 2.8 × 10−4 dB km−1.

Numerical investigation of high birefringence and nonlinearity tellurite glass photonic crystal fiber with microstructured core.

In this paper, a novel photonic crystal fiber (PCF) based on tellurite glass with high birefringence and high nonlinearity is designed. Six small air holes arranged nearly rectangularly are added in the fiber core to form the near-elliptic core. By using the finite-element method with the help of COMSOL Multiphysics software, we investigate and simulate the birefringence, effective mode area, nonlinear coefficient, and the dispersion characteristics. Simulation results show that by optimizing the structure parameters of the core, at the wavelength of 1.55 µm, the birefringence is up to ${5.05} \times {{1}}{{{0}}^{- 2}}$; the nonlinear coefficient can reach a maximum of ${{1896}}\;{{\rm{W}}^{- 1}}\;{\rm{k}}{{\rm{m}}^{- 1}}$; moreover, the zero dispersion points can be obtained around the wavelength 1.55 µm. The proposed structure is easy to fabricate. The advantage of the proposed PCF has potential applications in polarization control, communication systems, and supercontinuum generation.

Wide range refractive index sensor using a birefringent optical fiber

In this article, an efficient high birefringent D-shaped photonic crystal fiber (HB-D-PCF) plasmonic refractive index sensor is reported. It is able to work over a long low refractive index analyte range from 1.29 to 1.36. This modified simple structured hexagonal PCF has high birefringence in the near-infrared region. A thin gold film protected by a titanium dioxide (TiO2) layer is deposited on the D-surface of the PCF which acts as surface plasmon active layer. The sensor consists of an analyte channel on the top of the fiber. The performance of the HB-D-PCF is analyzed based on finite element method. Both wavelength and amplitude interrogation techniques are applied to study the sensing performance of the optimized sensor. Numerical results show wavelength and amplitude sensitivity of 9245 nm/RIU and 1312 RIU−1 respectively with high resolution. Owing to the high sensitivity, long range sensing ability as well as spectral stability the designed HB-D-PCF SPR sensor is a potential candidate for water pollution control, glucose concentration testing, biochemical analyte detection as well as portable device fabrication.

Highly birefringent photonic crystal fiber with D-shaped air holes for terahertz (THz) application

Abstract A new type of high birefringence terahertz (THz) band photonic crystal fiber (PCF) is proposed. D-shaped air holes are introduced into the core of the PCF and the cladding near the core. Some important parameters of this waveguide were researched in the range of 0.6–1.2 THz. The simulation results show that the proposed fiber has a high birefringence of 0.0425 at 0.7 THz. In addition, the confinement loss and the effective mode area are respectively 6.63 × 10−7 dB/m and 0.77 × 105 μm2, when the operating frequency is 1 THz and the high birefringence of 0.04 is maintained. At the same time, very low bending loss and near zero flat positive dispersion are obtained. And has single-mode operating characteristics in the entire research frequency range. The PCF structure will provide new solutions for the application of THz waves and the design of THz waveguides.

Bend-Insensitive Discrimination of Strain and Temperature Based on Fiber Transmission Grating Inscribed on High Birefringence Photonic Crystal Fiber.

In this paper, we propose a bend-insensitive optical fiber sensor capable of separately measuring strain and temperature by incorporating a fiber transmission grating (FTG) inscribed on high birefringence photonic crystal fiber (HBPCF) with a CO2 laser. The FTG was fabricated by exposing unjacketed HBPCF to CO2 laser pulses using the line-by-line technique. The FTG inscribed on HBPCF, referred to as the HBPC-FTG, has two resonance dips with different wavelengths depending on input polarization. These two resonance dips were utilized as sensor indicator dips denoted by a shorter wavelength dip (SD) and a longer wavelength dip (LD). The strain and temperature responses of the SD and LD were investigated in a strain range of 0 to 3105 μ and a temperature range of 30 to 85 °C, respectively. The measured strain sensitivities of the SD and LD at room temperature (25 °C) were approximately -0.46 and -0.58 pm/μ, respectively. Similarly, the measured temperature sensitivities of the SD and LD without applied strain (0 μ) were ˜5.99 and ˜9.89 pm/°C, respectively. Owing to their linear and independent responses to strain and temperature, strain and temperature changes applied to the HBPC-FTG can be simultaneously estimated from the measured wavelength shifts of the two indicator dips (i.e., SD and LD) using their predetermined strain and temperature sensitivities. Moreover, bend-induced spectral variations of the SD and LD were also examined in a curvature range of 0-4.705 m-1, and it was observed that both dips showed little wavelength shift due to applied bending. Thus, it is concluded from the experimental results that the fabricated HBPC-FTG can be employed as a cost-effective sensor head for bend-insensitive discrimination of strain and temperature.

A highly birefringent bend-insensitive porous core PCF for endlessly single-mode operation in THz regime: an analysis with core porosity

We present an endlessly single-mode, bend-insensitive and highly birefringent photonic crystal fibre (PCF) for efficient wave transmission in the terahertz (THz) spectrum. To facilitate flat dispersion and high birefringence, a diamond-shaped porous core is introduced inside the Zeonex (background material)-based hexagonal porous cladding. Moreover, the dense geometrical arrangement of the regular hexagonal lattice in the cladding region holds maximum usable optical power inside the porous core. The major geometrical parameter of the proposed PCF such as core porosity has been optimized to improve the optical guiding parameters. The numerically investigated outcomes have shown an ultrahigh birefringence and numerical aperture of 0.0888 and 0.57, respectively. Apart from this, very low bending and material losses of $$3.01 \times 10^{ - 20}$$ cm−1 and 0.01451 cm−1 with flattened dispersion variation of ± 0.2463 ps/THz/cm have been achieved over the broad THz band (i.e. 0.8–1.3 THz). Additionally, our proposed PCF sustains endlessly single-mode operation with a very high core power fraction of 75.28%. With all these promising results, the proposed PCF would be a potential candidate for polarization preserving as well as for efficient broadband transmission applications in the THz regime.

A Novel Ultra-high Birefringent Photonic Crystal Fiber for Nonlinear Applications

In this paper, a novel polarization-maintaining highly birefringent photonic crystal fiber (PMHB-PCF) has been investigated by using finite element method (FEM). Initially, the numerical analysis is carried out to ascertain its PMHB characteristics by using two different novel PCF structures (hexagonal-elliptical PCF and elliptical-elliptical PCF) and their performance characteristics are measured. By inducing the asymmetries in the fiber structure, the beat length of the fiber and their modal birefringence have been optimized. In proposed designs hexagonal-elliptical (cladding layers) PCF structure provides an ultra-high birefringence of about 4.51 × 10–2 with a lower beat length of 34.37 µm. This reported fiber exposed a high nonlinear coefficient of about 61. 95 W−1 km−1 at the operating wavelength of 1.55 µm. Also, it has a normalized frequency parameter (V parameter) of about 1.373 over the optical spectrum of 1.3 to 1.6 µm; it ensures the fiber single-mode operation. Due to the high nonlinearity and birefringence, this fiber is more suitable for nonlinear applications. It confirms the phase-matching conditions for the purpose like wavelength conversion which employs four-wave mixing technique.

High birefringence and broadband dispersion compensation photonic crystal fiber

Abstract We propose a perfectly square lattice photonic crystal fiber (PCF) which shows high birefringence and negative dispersion. To set up high asymmetry in the core, dual line imperfection is considered where the fill fraction ratio and defect air hole diameter exhibit significant impact on dispersion and birefringence. Numerical analyses of guiding properties of the proposed PCF are done using finite element method with perfectly matched layer boundary condition from 1.2 to 1.8 μm wavelength. The optimized square lattice PCF presents high birefringence of 2.48 × 10−2 and dispersion of −777.66 (ps/nm.km) at 1.55 μm wavelength. In addition, the proposed PCF offers ultra-low confinement and insertion loss at 1.55 μm wavelength. Moreover, −0.45 (ps/nm2.km) dispersion slope and 0.0045 nm−1 relative dispersion slope are observed at 1.55 μm wavelength. Additionally, the proposed PCF maintains dispersion and birefringence variation of ±30 (ps/nm.km) and ±0.00001 between 1.5 and 1.6 μm wavelength ranges, respectively. Furthermore, the proposed PCF shows high quality factor and low bit error rate at 10 dBm input power. We believe the proposed square lattice PCF can be deployed in wavelength division multiplexing based optical fiber transmission system for wide-band dispersion compensation.

Highly sensitive near-infrared surface plasmon resonance (SPR) sensor based on birefringent six-core photonic crystal fibre

A new type of highly sensitive near-infrared birefringent six-core photonic crystal fibre sensor using surface plasmon resonance (SPR) is proposed. By using the full-vector finite element method, the impacts of the fibre parameters on the wavelength sensitivity and amplitude sensitivity are numerically studied. The numerical results indicate that, benefiting from the high birefringent multi-core fibre structure, an average sensitivity of 8083 nm/refractive index unit (RIU) within the wavelength range from 1.532 to 2.02 µm is achieved when the analyte refractive index (RI) lies in (1.372, 1.432). Moreover, the maximum amplitude sensitivity is as high as 226 RIU−1 if the analyte RI is adjusted from 1.372 to 1.382. In consideration of its excellent sensing performance, the proposed SPR multi-core PCF sensor can be applied in environmental, food safety, and (bio)chemical detection.

Design and Analysis of High Birefringence Photonic Crystal Fiber with Sandwich Structure

A novel photonic crystal fiber (PCF) with sandwich structure in cross section is proposed. Then the influences of the size of air holes in cladding on the propagation properties are investigated. By adjusting the size of air holes in cladding, the proposed PCF offers an ultrahigh birefringence of 3.85 × 10-2 and a large negative dispersion of - 1000 ps·km-1·nm-1 for the optimal structure of the fiber at the wavelength of 1550nm. The nonlinear coefficient of the optimal structure can reach a large value about 50W-1 ·km-1 at the wavelength of 1550nm. The proposed PCF may have some potential applications in the fields of long-distance optical communication and polarization maintaining fiber.

Surface plasmon enhanced polarization filter of high birefringence photonic crystal fiber with a partial core based on filled silver nanowire

Abstract A novel kind of near-infrared communication window of photonic crystal fiber (PCF) polarization filter based on filled silver nanowire is proposed in this paper. The silver nanowire is selectively filled in a air hole of the cladding, and the performance of this PCF is analyzed by changing the diameter d2 of the near-core small air holes by finite element method (FEM). It is found that the confinement loss of x-polarization is 10738.726 dB/m, and that of y-polarization is 272.2325 dB/m at the resonance wavelength of 1.24 μm when the diameter d2 = 0.3 μm. Furthermore, when the fiber length is 1 mm, the crosstalks of x and y-polarization are −90.9 dB and 85 dB at the resonance wavelength of 1.24 μm and 1.32 μm, respectively. Thus, it can well realize the function of polarization filtering in two communication bands.

Simulation of a highly birefringent photonic crystal fiber in terahertz frequency region

We have designed a Photonic Crystal Fiber (PCF) to achieve high birefringence optical property in the terahertz (THz) frequency region. Air holes look like rectangular shape in cladding area and elliptical air hole in the center zone are considered for the proposed PCF. To identify loss characteristics of the proposed PCF, effective material loss (EML) and confinement loss also have been studied in this paper. The commercial optical properties analyzer, COMSOL Multiphysics 5.3a software has been used for numerical analysis of the designed PCF. To obtain the optimal PCF structure properties, we have varied the elliptical shaped air holes major axis length and adjacent ellipse pitch distance. Numerical analysis shows the maximum birefringence of 0.0921 and minimum confinement loss of $$1.36\, \times 10^{-4} \hbox {cm}^{-1}$$ for the proposed PCF. We hope that this highly birefringent PCF will contribute in the field of polarization filter, bio-sensing and terahertz communication devices.

Photonic crystal fibers with high birefringence and multiple zero dispersion wavelengths

Abstract A type of total internal reflection photonic crystal fiber (TIR-PCF) with high birefringence and multiple zero dispersion wavelengths is presented. The optical characteristics are numerically investigated by using the full-vector finite element method. Results show that, by setting the geometrical parameters, the mode birefringence can reach to 2.28 × 10−2 at the wavelength of 1.55 μm, and two zero-dispersion wavelength points appear in the infrared band, one of which emerges near the wavelength of 1.55 μm. It provides a new structure for large birefringence photonic crystal fiber with multiple zero-dispersion wavelengths, and it could be widely used in the fields of fiber polarization control, dispersion management, super-continuum generation and soliton propagation.