Md. Imran Hasan

Ultra-Low Material Loss and Dispersion Flattened Fiber for THz Transmission

This letter reports a photonic crystal fiber having ultralow material loss and near-zero dispersion at the telecom window which is suitable for THz wave guidance. The finite element method with perfectly matched layer circular boundary is used to investigate the guiding properties. The numerical results show that ultra-low material absorption loss of 0.056 cm-1 at 1.0 THz and nearly zero flattened dispersion of ±0.18 ps/THz/cm can be obtained from the proposed fiber in the wavelength range of 1.0-1.8 THz.

Tellurite glass defect-core spiral photonic crystal fiber with low loss and large negative flattened dispersion over S + C + L + U wavelength bands

A defected-core spiral photonic crystal fiber is proposed to achieve very large negative flattened dispersion and small confinement loss. Simulation results reveal that the designed structure exhibits very large flattened dispersion over S+C+L+U wavelength bands and an average dispersion of about -720.7  ps nm(-1) km(-1) with an absolute dispersion variation of 12.7  ps nm(-1)  km(-1) over the wavelength ranging from 1.45 to 1.65 μm. The proposed fiber has five air-hole rings in the cladding leading to very small confinement loss of 0.00111  dB/km at the excitation wavelength of 1.55 μm. The tolerance of the fiber dispersion of ±2% changing in the structural parameters is investigated for practical conditions.

Design and Characterization of Highly Birefringent Residual Dispersion Compensating Photonic Crystal Fiber

A residual dispersion compensating octagonal photonic crystal fiber (OPCF), with an elliptical array of circular air-holes in the fiber core region, is proposed. The full-vector finite-element method with perfectly matched layer boundary is used as the analysis tool. It is demonstrated that it is possible to obtain large average negative dispersion of -562.52 ps/(nm · km) over 240 nm and -369.10 ps/(nm · km) over 630 nm wavelength bands for the fast and the slow axis, respectively. In addition to large negative dispersion, ultra-high birefringence, high nonlinearity, and zero-dispersion wavelengths with low confinement loss are also warranted. The proposed OPCFs would be a promising candidate for residual dispersion compensation, supercontinuum generation, and other applications.

Polarization Maintaining Low-Loss Slotted Core Kagome Lattice THz Fiber

A polarization maintaining ultra-low effective material loss based on slotted core kagome lattice fiber is proposed for terahertz (THz) wave propagation. Numerical study demonstrates that by using rectangular slotted air holes in the core of the kagome lattice exhibits simultaneously an ultra-high birefringence of 8.22 × 10-2, an ultra-low effective material loss of 0.05 cm-1, and a very low confinement loss of 4.13×10-5 cm-1 at the frequency of 1 THz. Further investigation shows that about half of the total mode power confines into the air slots at 50% core porosity. The proposed fiber can be used for polarization maintaining applications in THz regime.

A single-mode highly birefringent dispersion-compensating photonic crystal fiber using hybrid cladding

Abstract Based on the hybrid cladding design, a single-mode photonic crystal fibre (PCF) is proposed to achieve an ultra-high birefringence and large negative dispersion coefficient using finite-element method. Simulation results reveal that with optimal design parameters, it is possible to achieve an ultra-high birefringence of 2.64 × 10−2 at the excitation wavelength of 1.55 μm. The designed structure also shows large dispersion coefficient about −242.22 to −762.6 ps/nm/km over the wavelength ranging from 1.30 to 1.65 μm. Moreover, residual dispersion, effective dispersion, effective area, confinement loss and nonlinear coefficient of the proposed PCF are discussed thoroughly.

A Polarization Maintaining Single-Mode Photonic Crystal Fiber for Residual Dispersion Compensation

A single-mode octagonal photonic crystal fiber (OPCF) is proposed to simultaneously achieve high birefringence and ultra-flattened ultra-high negative dispersion. Simulation results demonstrate that by introducing an elliptical air hole in the center of the core, it is possible to obtain a large average dispersion of -608.93 ps/nm/km with an absolute dispersion variation of -12.7 ps/nm/km over 1.46-1.625 μm wavelength bands for fundamental slow-axis mode. Besides, with optimal design parameters, a high birefringence of 1.81×10-2 and a very low confinement loss of 0.04 dB/km are achieved at 1.55 μm. The proposed OPCF can be used in cost-effective residual dispersion compensation and optical sensors.

Relative dispersion slope matched dispersion compensating highly birefringent spiral microstructure optical fibers using defected core

Abstract. A highly birefringent dispersion compensating microstructure optical fiber (MOF) based on a modified spiral (MS)-MOF is presented that successfully compensates the dispersion covering the E- to L-communication bands ranging from 1370 to 1640 nm. It is shown theoretically that it can obtain a negative dispersion coefficient of about −221 to −424  ps/(nm·km)) over S to L bands and −327  ps/(nm· km)) at the operating wavelength of 1550 nm. The relative dispersion slope is perfectly matched to that of single-mode fiber of about 0.0036  nm−1. Besides, the proposed MS-MOF offers high birefringence of 1.79×10−2 with a large nonlinear coefficient of about 41.8  W−1 km−1 at the operating wavelength along with two zero dispersion wavelengths at 610 and 1220 nm. Futhermore, the variation of structural parameters is also studied to evaluate the tolerance of the fabrication.

Polarization maintaining highly nonlinear photonic crystal fiber with closely lying two zero dispersion wavelengths

Abstract. A simple hexagonal photonic crystal fiber is proposed to simultaneously achieve ultrahigh birefringence, large nonlinear coefficient, and two zero dispersion wavelengths (ZDWs). The finite element method with circular perfectly matched layer boundary condition is used to simulate the designed structure. Simulation results show that it is possible to achieve two closely lying ZDWs of 1.08 and 1.29  μm for x-polarization with 0.88 and 1.20  μm for y-polarization modes, respectively. In addition, an ultrahigh birefringence of 3.15×10−2 and a high nonlinear coefficient of 58  W−1 km−1 are also obtained at the excitation wavelength of 1.55  μm. The proposed fiber can have important applications in supercontinuum generation, parametric amplification, four-wave mixing, and optical sensors design.

Design and simulation of a low cost three band microstrip patch antenna for the X-band, Ku-band and K- band applications

The aim of this paper is to design the effective shape of a microstrip patch antenna which can provide lower return losses, better gain and performance for X-band (2 GHz to12 GHz), Ku-band (12 GHz to 18 GHz) and K-band (18 GHz to 26 GHz) applications. Attempts have been made to optimize the antenna performance by increasing the number of slots, by using slots in different position in patch and by using array technique. The simulation is performed by using GEMS simulator which is commercially available antenna simulator. The antenna is designed by using Taconic TLY-5 dielectric substrate with permittivity □r =2.2 and height, h=1.588 mm. Without using array technique we have got the return losses in the range of -20 db to -25 db at the frequencies around 19.5 GHz. The series feed array offers -7.25 db return loss around 11.5 GHz, -17.5 db return loss around 16 GHz and -13db return loss around 21GHz. Therefore, this antenna is suitable for X-band, Ku-band and K- band applications.

Tailoring polarization maintaining broadband residual dispersion compensating octagonal photonic crystal fibers

Abstract. We present a residual dispersion compensating highly birefringent photonic crystal fiber (PCF) based on an octagonal structure for broadband dispersion compensation in the wavelength range 1460–1625 nm. The finite element method with perfectly matched boundary condition is used as the numerical design tool. It has been shown theoretically that it is possible to obtain a negative dispersion coefficient of about −418 to −775  ps/nm/km over the S-, C-, and L-bands, relative dispersion slope (RDS) close to that of single mode fiber (SMF) of about 0.0036  nm−1 at 1550 nm. According to the simulation, birefringence of 2×10−2 is obtained at 1550-nm wavelength. The variation of structural parameters is also studied to evaluate the tolerance of the fabrication. The proposed octagonal PCF can be a potential candidate for residual dispersion compensation as well as maintaining single polarization in optical fiber transmission system.