Md. Rabiul Hasan

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.

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.

Photonic crystal fiber-based plasmonic biosensor with external sensing approach

Abstract. We propose a simple photonic crystal fiber (PCF) biosensor based on the surface plasmon resonance effect. The sensing properties are characterized using the finite element method. Chemically stable gold material is deposited on the outer surface of the PCF to realize the practical sensing approach. The performance of the modeled biosensor is investigated in terms of wavelength sensitivity, amplitude sensitivity, sensor resolution, and linearity of the resonant wavelength with the variation of structural parameters. In the sensing range of 1.33 to 1.37, maximum sensitivities of 4000  nm/RIU and 478  RIU−1 are achieved with the high sensor resolutions of 2.5×10−5 and 2.1×10−5  RIU using wavelength and amplitude interrogation methods, respectively. The designed biosensor will reduce fabrication complexity due to its simple and realistic hexagonal lattice structure. It is anticipated that the proposed biosensor may find possible applications for unknown biological and biochemical analyte detections with a high degree of accuracy.

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.

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.

Low-loss and bend-insensitive terahertz fiber using a rhombic-shaped core

A novel porous-core photonic crystal fiber is presented, and its guiding properties are numerically investigated by using the finite element method. It is demonstrated that by introducing a rhombic-shaped core made of circular air holes inside the conventional hexagonal cladding, it is possible to obtain very low bending loss of 3.04×10-11  cm-1 at the operating frequency of 1.0 THz. In addition to this, low effective material loss of 0.089  cm-1 and very small confinement loss of 1.17×10-3  dB/cm are achieved for optimal design parameters. Other guiding properties, including effective area, dispersion, and higher order mode characteristics are also discussed thoroughly. The design of this porous fiber is relatively simple, since it contains fewer air holes and consists of circular air holes only. Due to promising wave-guiding properties, the proposed fiber would have a great potential for terahertz imaging and flexible communication applications.

Dual-hole unit-based kagome lattice microstructure fiber for low-loss and highly birefringent terahertz guidance

Abstract. A low-loss microstructure fiber is numerically investigated for convenient transmission of polarization maintaining terahertz (THz) waves. The dual-hole units (DHUs) are used inside the core of the kagome lattice microstructure to achieve high birefringence and low effective material loss (EML). It is demonstrated that by rotating the axis of orientation of the DHUs, it is possible to obtain low EML of 0.052  cm−1, low confinement loss of 0.01  cm−1, and high birefringence of 0.0354 at 0.85 THz. It is also reported that the transmission properties of the proposed microstructure fiber are varied with rotation angle, core diameter, and operating frequencies. Other guiding characteristics, such as single-mode propagation, power fraction, and dispersion, are also discussed thoroughly.

Ultra-flattened negative dispersion for residual dispersion compensation using soft glass equiangular spiral photonic crystal fiber

Abstract We present a numerical investigation of an equiangular spiral photonic crystal fibre (ES-PCF) in soft glass for negative flattened dispersion and ultra-high birefringence. An accurate numerical approach based on finite element method is used for the simulation of the proposed structure. It is demonstrated that it is possible to obtain average negative dispersion of –526.99 ps/nm/km over 1.05–1.70 μm wavelength range with dispersion variation of 3.7 ps/nm/km. The proposed ES-PCF also offers high birefringence of 0.0226 at the excitation wavelength of 1.55 μm. The results here show that the idea of using the proposed fibre can be potential means of effectively directing for residual dispersion compensation, fibre sensor design, long distance data transmission system and so forth.

Design of a surface plasmon resonance refractive index sensor with high sensitivity

This paper presents a highly sensitive photonic crystal fiber (PCF) refractive index sensor based on the surface plasmon resonance (SPR) effect operating in the telecommunication wavelengths. Gold is used as the plasmonic material due to its chemical stability and titanium dioxide (TiO2) is used to shift the resonance wavelength in the telecommunication bands. Both materials are deposited sequentially on the PCF surface, which is comparatively easy to fabricate. Numerical investigations show that the proposed sensor exhibits very high wavelength sensitivity of 10,800  nm/RIU and amplitude sensitivity of 514  RIU−1 in the sensing range between 1.46 and 1.48. Moreover, it exhibits maximum sensor resolution of 9.25×10−6  RIU and high linearity over a wide sensing range. The proposed sensor can be practically realized due to its simple and straightforward structure.