M. Shah Alam

Bangladesh University of Engineering and Technology | BUET · Department of Electrical and Electronic Engineering

Two structures of circular lattice Photonic Crystal Fibers (PCFs) based on Ge20Sb15Se65 (GSS) material have been proposed for a highly coherent broadband supercontinuum generation (SCG) in the mid-infrared region. Numerical studies using the Finite Difference Eigenmode (FDE) solver on both structures show that the fundamental modes are well confine...

A promising 2-mm-long highly coherent air-clad suspended core planar Si-rich SiN tapered waveguide is proposed for supercontinuum generation in the midinfrared. Supercontinuum evolution is investigated by tuning the waveguide for both of the transverse-electric (TE) and transverse-magnetic (TM) polarizations employing pump at 1.55 m with a pulse du...

In this research paper, we propose a highly sensitive yet simple design hexagonal photonic crystal fiber (PCF) core-based surface plasmon resonance (SPR) refractive index (RI) sensor. The unknown target analyte and the plasmonic material, gold (Au) are placed at the exterior of the sensor surface for the feasibility of the operation. Twelve purely...

In this work, we have designed two simple photonic crystal fibers (PCFs) with the highly nonlinear chalcogenide material of Ge11.5As24Se64.5 for broadband mid-infrared supercontinuum generation. The hexagonal lattice of air holes in a star type arrangement has been considered in the designs, where only two different air hole sizes and a constant pi...

A detailed investigation is performed to obtain optimized optical performance of polar III-nitride single quantum well (SQW) semiconductor Lasers by band engineering through symmetric and asymmetric tuning of device parameters. Electronic, optical, and threshold characteristics are calculated to analyze the effects of band engineering on device per...

In this work, a graphene hybrid plasmonic waveguide has been studied employing the finite element method. The graphene layers have been exploited here as optical absorber layers to extinguish the undesired plasmon modes in our system. Also, the silicon nanowires in our design, have been utilized to form a hybrid plasmon waveguide in order to achiev...

In this work, nanowire-based symmetrical graphene hybrid plasmonic waveguides for possible broadband optical modulation have been proposed. The full-vectorial finite element method has been employed to analyze the modal properties and modulation characteristics of the proposed structures. The fundamental supermode supported by these geometries is e...

A highly birefringent polarization-maintaining dual-core photonic crystal fiber (DC-PCF) structure with elliptical air holes around the cores has been designed for possible supercontinuum generation over two octaves spanning a spectral bandwidth in the 400- to 1800-nm wavelength range. The supercontinuum (SC) spectrum covers the near-UV, visual, an...

Optical capacitance effect and metal-insulator-metal mode coupling have been exploited in this work to enhance the light-graphene interaction. Hence, large extinction ratio and high modulation bandwidth are achieved simultaneously.

A hybrid plasmon waveguide comprising with metal and dielectric nanowires has been investigated employing the finite element method. At the telecommunication wavelength, strong SPP-dielectric mode coupling in this structure gives rise to capacitor like electromagnetic energy localization in the dielectric gap with extremely low effective area (~λ 2...

In this work, a hybrid plasmonic waveguide containing the elliptical nanowires of gold and ZnO with a low index dielectric cladding has been analyzed using the finite element method. The fundamental mode obtained here has been reported to offer a remarkably small effective area $(\sim\lambda^{2}/80)$ with a very high electromagnetic energy confinem...

Modal properties of a plasmon guiding structure consisting of two parallel metallic nanowires embedded in a dielectric material have been analyzed employing the finite element method. The coupling characteristics of the surface plasmon supermode reveal extreme yet linearly changing confinement for a moderate range of nanowire separation. The potent...

In this paper, the resonance and radiation characteristics of patch antennas fabricated with two different types of dielectric substrates have been investigated and compared at GSM 1800 MHz band. At first, the above-stated characteristics of a patch antenna loaded with conventional plastic substrate have been investigated. Later a high permittivity...

A single quantum well semiconductor laser based on wurtzite-nitride is designed and analyzed for short distance communication wavelength (at around 1300 nm). The laser structure has 12 Å well layer of InN, 15 Å barrier layer of In0.25Ga0.75N, and 54 Å separate confinement heterostructure layer of GaN. To calculate the electronic characteristics of...

This paper presents different properties of silicon nanowire when a hole of sub-wavelength diameter is introduced in the central region. The analysis has been carried out using edge element based vector finite element method (FEM). It has been found that the light enhancement and the average mode intensity are higher within smaller holes. The nonli...

A nitride based wurtzite-strained QW laser with 12Å InN well layer, 15Å In0.25Ga0.75N barrier layer and GaN SCH layer has been designed and characterized at 1330nm wavelength. To determine the electronic properties, a self-consistent method with 6-bands k.p formalism considering valence-band mixing effect, strain and polarization effect followed by...

An AlGaN based quantum well laser with GaN delta layer and AlN barrier layers has been designed and characterized for obtaining electronic and optical characteristics. The band structure was calculated with self-consistent 6-band k.p formalism including valence-band mixing effect, strain and polarization effect. A Genetic Algorithm based optimizati...

In this work, a nitride based wurtzite-strained single quantum well laser has been designed and characterized at 1330 nm wavelength. Here, 12Å InN layer has been used as well material and 15Å In 0.25 Ga 0.75 N layer has been used as barrier material along with GaN as separate confinement heterostructure for better carrier and optical confinement. T...

In this work, AlGaN based quantum well laser has been designed with delta layer and characterized the designed laser structure. After the characterization, Genetic Algorithm process has been performed over optical gain to optimize it. In this design, AlN has been used as barrier material, Al 0.8 Ga 0.2 N has been utilized as active region material...

A band edge cavity on ferroelectric Barium Titanate is proposed. The cavity is designed by inserting a Photonic Crystal (PhC) within another PhC, so that the band edge of the core PhC falls within the bandgap of the outer PhC, which supports the slow light modes of the inner PC. The PhCs are selected based on their band diagram which is calculated...

The concept of employing a central air hole in the core is exploited to obtain an ultralarge negative dispersion photonic crystal fiber (PCF) over the wavelength range of 1350 to 1650 nm. The results show that the fiber may exhibit an average dispersion well over -500 ps/nm-km with a flattened dispersion profile. It is also found that the fiber sho...

The electronic and optical properties of tetragonal barium titanate (BaTiO3) have been investigated by use of first-principles density functional theory on a plane wave basis, by use of norm-conserving pseudopotentials in the localized density approximation. For accuracy, experimental lattice parameters reported in the literature were used. The ban...

In this work, a nitride based strained single quantum well laser has been designed and characterized at 1330 nm wavelength. Here, InN has been used as well material and InGaN has been used as barrier material along with GaN as separate confinement heterostructure for better carrier and optical confinement. For the analysis of characteristics of the...

We demonstrate low loss (0.4043 dB/Km at 1.55 μm) deep sub-wavelength broadband evanescent field confinement in low index material from near IR to mid IR wavelengths with the aid of an specialty optical fiber whilst achieving at least 1.5 dB improvement of figure of merit over the previous design. Plane strain analysis has been conducted to foresee...

A surface plasmon resonance (SPR) sensor design based on four-core square lattice photonic crystal fiber (SL-PCF) has been proposed in this work. The fundamental coupling properties between the core guided light and surface plasmon polaritons are investigated here by using the finite element method (FEM). It is found that the phase matching phenome...

A technique of mitigating the reduction of mode area in bent large mode area (LMA) fibers by employing higher index rods in one region of the core along with lower index microstructured rods at the opposite region has been presented in this paper. The effective area is further increased by lowering the index difference between the background and so...

A band edge cavity on ferroelectric Barium Titanate is proposed. The cavity is designed by inserting a Photonic Crystal (PhC) within another PhC, so that the band edge of the core PhC falls within the band-gap of the outer PhC, which supports the slow light modes of the inner PC. The PhCs are selected based on their band diagram which is calculated...

The leakage losses of a bent equiangular spiral photonic crystal fiber (ES-PCF) have been analyzed in this paper by employing a full-vectorial finite element method. The analysis shows that the confinement and bending losses of ES-PCF are several orders of magnitude less than that of the conventional hexagonal lattice PCF (H-PCF) with similar dimen...

We designed a photonic double heterostructure cavity on rectangular lattice with an incorporated slot waveguide, which shows high quality factor for both TE and TM modes despite an absence of complete bandgap. The confinement capability of the cavity has been studied using the finite difference time domain method. The ferroelectric barium titanate...

A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies...

In this work, mechanical and optical characterization of a new type of suspended core fiber (SCF) has been performed. The proposed SCF along with additional central air holes exhibits an unusual property of fundamental mode cutoff at short wavelengths. Two variants (single hole and double hole) of design under two different fiber platforms (SiO2 an...

We propose a novel type of photonic crystal cavity with a flattened and elongated central hole. The confinement capability of the cavity for the TE mode is studied using the 2D-FDTD method. The holes immediately around the cavity are shifted in a space modulation scheme in order to optimize the confinement capability of the proposed cavity. The cha...

We investigate the electronic and optical properties of InP in the zincblende phase using a plane wave basis with local density approximation (LDA). The Kohn Sham bandstructure of InP is obtained, from which the bandgap of the material is calculated. The density of states (DOS) of the two atoms of InP are also obtained. The complex dielectric funct...

We have designed and studied the confinement capability of a defect cavity on a curvilinear lattice photonic crystal using finite domain time difference (FDTD) method. Gallium arsenide has been used as the base material, where the nonlinear and dispersive nature of the material have been taken into account. The resonant transverse magnetic (TM) and...

A dispersion compensating fiber having average dispersion profile of -259 ps/nm-km with dispersion variation of about 4.58 ps/nm-km has been obtained over the wavelength range 1.35 μm to 1.675 μm using an equiangular spiral photonic crystal fiber (ES-PCF). The proposed fiber also exhibits single polarization behavior with one of its fundamental mod...

The design of a residual dispersion compensating fiber in an equiangular spiral photonic crystal fiber (ES-PCF) structure is presented in the wavelength range 1350-1650 nm. A step-by-step design optimization is demonstrated and a maximum optimized value of average dispersion - 393 ps/nm km with a flattened dispersion profile with a very high birefr...

An equiangular spiral photonic crystal fiber has been designed and numerically optimized to obtain its residual chromatic dispersion compensation property in the wavelength range of 1350–1675 nm. The results show that the fiber exhibits an average dispersion of ${-}{\rm 227}~{\rm ps}/{\rm nm}\hbox{-}{\rm km}$ with a flattened dispersion profile. It...

The quasi-TEM finite element analysis of microwave and optical devices has been carried out in this work. The static approach that involves the solution of Laplace’s equation can be utilized to characterize many important properties of microstrip lines, microshield lines, and microwave photonic components. In this work, we have incorporated such an...

Silicon nanowires on silica cladding have been simulated using finite element method in this paper. The transverse and longitudinal electric field patterns are analyzed and it has been observed that a smaller core dimension results in a larger longitudinal field. Also, dispersion engineering through configuring the nanowire structure has been discu...

A silica spiral photonic crystal fiber is presented here for tailoring two zero dispersion wavelengths (ZDWs) in the visible region. The proposed fiber has two ZDWs (523.1 and 716.8 nm) along with a very high nonlinearity parameter (1060 W-1 km-1 at 500 nm) around the visible region. The proposed design shows improvement over the group dispersion c...

Propagation characteristics of an elliptical hollow core optical fiber (EHOF) have been investigated under the application of high lateral and hydrostatic stresses. The simulation results exhibit significant effects of stress on birefringence, polarization mode dispersion (PMD), group velocity dispersion, effective area, and power confinement. High...

A highly nonlinear suspended core fiber (SCF) has been proposed, where a geometrical design parameter called suspension factor (SF) has been used for dispersion tailoring in the infrared region ( 1.2 μm to 2.8 μm ). We have investigated the effect of different suspended conditions of the SCF core on group velocity dispersion, fiber nonlinearity, an...

In this paper, a numerical study of optical performances of chalcogenide based PCFs with hexagonal and ‎octagonal symmetry has been performed in the mid-IR spectrum for the first time. A tapering factor has been ‎introduced to investigate the effects of core size for both the cases. Qualitative analysis of group velocity dispersion ‎has been presen...

An analytic equation has been proposed to realize propagation charac-teristics for different geometrical patterns of ‎silicon nanowire using full vector FEM. Analysis of mode dependent nonlinear loss has revealed that attenuation ‎of sig-nal power is less for higher order modes than for the fundamental modes excited in the nanowire.‎

In this paper, we have proposed a novel nano-photonic device for nonlinear applications in the visible range. The ‎proposed device is a photonic crystal fiber nanowire composed of highly transparent silica with a germania doped ‎silica as core material. Numerical analysis has confirmed that the proposed nonlinear device has a maximum ‎Raman gain co...

An analysis of a GaAs/AlGaAs electrooptic intensity modulator is carried out by using the finite element method. The microwave properties, e.g., the effective index, the characteristic impedance, and the frequency dependent attenuations are calculated using quasi-TEM analysis. The 3-dB optical bandwidth is estimated and it is shown that microwave l...

In this paper, sensitivity models for centre frequency and maximum radiated power of a rectangular microstrip antenna at φ = 0 plane using Effective Length Theory have been developed. A wide operating bandwidth for a single-layer coaxially fed microstrip antenna is obtained by cutting a U shaped slot on the metal patch. The sensitivity of perturbat...

In this paper, we have designed rectangular waveguides with discontinuities to analyze and improve their performance by using finite element solution method. Mathematical formulation is shown for the transverse electric mode for analyzing the waveguides. The analyses of some other wave properties (both electric and magnetic) of the designed rectang...

A liquid crystal infiltrated spiral photonic crystal fiber (LCSPCF) is presented here for electrical tuning of two zero dispersion wavelengths (ZDWs) in the present communication window. The proposed LCSPCF shows tunability of the ZDWs from 1433 nm to 2136 nm due to the rotation of the infiltrated LC mesogen induced by the external electric field....

A novel design of a single polarization fiber is proposed in this work. The fiber comprises an elliptical core with a central air-hole and side air holes. Analysis of different polarization properties of the newly designed fiber has been performed both with and without the presence of thermal stress. The investigation shows that the new design has...

Comparison between side-hole optical fiber and a new design of elliptical core fiber has been performed regarding the effect of thermal stress on different polarization. The new design comprises an elliptical core with central airhole and side air-holes. Simulation of these structures was carried out on the basis of finite element method. The analy...

In this paper, we have proposed a nonlinear photonic device and characterized linear and nonlinear optical properties from 1.5 μm to 5 μm using full vector finite element method. A sub-wavelength photonic wire inside a silica glass photonic crystal structure with an average index contrast ≈ 1.4 is found to maintain tight optical confinement at the...

A dispersion flattened, spiral silica photonic crystal fiber (SSPCF) is presented here for supercontinuum generation in the visible region. Two zero dispersion wavelengths (ZDWs) (570nm & 630nm) are obtained in the visible region for a core diameter of 600nm and the range of the anomalous dispersion increasing with the increment of the core diamete...

The effect of thermally induced stress on the modal properties of highly elliptical core optical fibers is studied in this work using a finite element method. The stress analysis is carried out and anisotropic refractive index change is calculated using both the conventional plane strain approximation and the generalized plane strain approach. Afte...

The external stress effect on the modal polarization properties of highly birefringent optical fibers is studied in this work using the finite element method. Examples of a side-hole fiber and a PANDA fiber have been considered in this work. The polarization mode dispersion in side-hole fiber usually increases with wavelength but, it increases furt...

Analysis of the effects of thermal and external stress on the properties of solid core photonic crystal fibers has been carried out in this work by using the finite element method. The external stress acting on the fiber induces a specific stress distribution on the fiber's cross section making the isotropic fiber material birefringent. The effecti...

A liquid crystal infiltrated spiral photonic crystal fiber (LCSPCF) is presented here for electrical tuning of two ‎zero dispersion wavelengths (ZDWs) in the present communication window. The proposed LCSPCF shows ‎tunability of the ZDWs from 1433 nm to 2136 nm due to the rotation of the director of the infiltrated LC ‎mesogen induced by the extern...

In this paper, we have characterized a mid-IR nonlinear photonic device consisting of a highly nonlinear As2Se3 ‎nanowire and a novel spiral photonic crystal structure on silica clad. The proposed photonic crystal fiber nanowire ‎‎(PCF-NW) structure has a number of parameters to control group velocity dispersion (GVD) for nonlinear ‎applications. T...

A highly nonlinear suspended core fiber (SCF) has been proposed, where a geometrical design parameter ‎called suspension factor (SF) has been used for dispersion tailoring in infrared region (1.2 m to 2.8 m). We ‎have investigated the effect of different suspended conditions of the SCF core on group velocity dispersion ‎‎(GVD), fiber nonlinearity...

The effect of external stress on polarization properties of a side-hole optical fiber is analyzed through stress analysis and optical mode analysis using finite element method. The dispersion properties are examined under two conditions: with thermal street and with hydraulic stress. The properties show similarity in both the conditions as the effe...

Highly birefringent elliptical hollow core optical fiber under hydrostatic pressure is analyzed in this work using finite element method. The combined effects of thermal stress generated during fabrication and external applied stress have been considered. Birefringence increases while group velocity dispersion decreases when the fiber is under hydr...

The effect of thermally induced stress on the fundamental and higher order modes of highly elliptical core optical fibers is studied in this work using a finite element method. The stress analysis is carried out and anisotropic refractive index change is calculated using the plain strain approximation. After considering the stress optical effect, t...

The analysis of traveling-wave electrooptic modulator on z-cut and x-cut lithium-niobate substrates is carried out using the finite element method based on a quasi-TEM approximation. The microwave effective index, characteristic impedance, and frequency dependent attenuations are calculated. Optical frequency response is also calculated and hence t...

A detailed microwave analysis of X-cut LiNbO3 (LN) electrooptical (EO) modulators is presented in this paper by using the finite element method (FEM). The two-step back-slot structure considered here satisfies the velocity matching condition and eliminates the necessity of buffer layer of silicon dioxide (SiO2) which is necessary for the ridge type...

A detailed modal analysis of photonic crystal fiber (PCF) is carried out by using the finite element method (FEM) in FEMLAB environment. The effective mode index of the fundamental mode is found out and the effective mode area is calculated for different PCF structures. Finally, dispersion property of different PCF structures is numerically calcula...

An analysis of birefringence properties of side-hole optical fibers has been presented in this work by using a finite element method. The birefringence caused by the thermal stress due to the different thermal expansion coefficients of core and cladding and also the geometrical birefringence are simultaneously considered. The validity of the calcul...

The bandwidth of traveling-wave electrooptic modulator on lithium niobate substrate is estimated by using the finite element method based on a quasi-TEM analysis. The microwave effective index, characteristic impedance, and loss are calculated. Optical frequency response is calculated and hence the bandwidth is estimated for velocity matching and i...

A review of the characterisation of optical guided-wave devices using modal solutions, junction analysis and the beam propagation method, based on the numerically efficient finite element method, is presented. Numerically simulated results for mode propagation in optical waveguides and the characterisation of various photonic devices, such as photo...

A numerical investigation of group birefringence is carried out on a recently reported highly birefringent hollow-core photonic bandgap fiber by use of an efficient vector finite-element method. The hollow fiber core has an area as large as that of approximately four airholes in the cladding region and assumes a rhombic shape with round corners, an...

Modal solutions for photonic crystal fibers with circular air-holes in a hexagonal array are presented, by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, modal hybridness, modal birefringence and group velocity dispersion values are presented. The effect of external pressure on...

Hybrid-mode propagation properties of multilayered and multiconductor transmission lines are studied by using an efficient vector finite element method (FEM) with high-order hybrid edge/nodal triangular elements, which can give frequency-dependent propagation constants directly. Characteristic impedances are also calculated from the FEM field solut...

The vector finite element method with hybrid edge/nodal triangular elements is extended for the analysis of lossy planar transmission lines. In order to handle lossy conductor transmission lines, the present approach includes the effect of finite conductivity of a lossy area, and the dissipations in metallic conductors and dielectrics are calculate...

The finite element method (FEM) with the high-order mixed-interpolation-type triangular element is used to solve the problem of practical microstrip lines with arbitrary metallization cross section. Analyses are carried out to produce the frequency characteristics of propagation constant, characteristic impedance, and attenuation constant of shield...