Third-order nonlinearities in optical waveguides have received considerable recent attention,1with particular interest in the possibility of devices for all-optical signal processing. In the small-intensity limit (linear case), field...
moreThird-order nonlinearities in optical waveguides have received considerable recent attention,1with particular interest in the possibility of devices for all-optical signal processing. In the small-intensity limit (linear case), field decomposition for longitudinally invariant lightguides allows for independently propagating modes, which are wave equation solutions after separation of transverse and longitudinal parts.2,3For intensity-dependent refractive indices, the illuminated guide is no longer longitudinally invariant, and thus this separation is not permitted. However, as is possible for tapered guides, we can describe the field as a combination oflocal modes,which couple as the light propagates. As local modes we can use modes of the linear-index guide. Alternatively, we may use solutions of the nonlinear wave equation (NLWE) for the transverse field dependence.4For approximate monomode propagation this can provide a more natural field representation in particular. However, these modes are only solutions of the transverse NLWE if considered in isolation; i.e., each nonlinear mode modifies the nonlinear index differently. For few-mode propagation, although a coupled nonlinear-local-mode approach may involve fewer local modes depending on the structure, increased complexity in the formalism results when non-orthogonality of the nonlinear modes is accounted for. In contrast, the linear-local-mode treatment has the attraction of simplicity. In Figs. 1-3 we consider the nonlinearly coupled linear-guide local-mode field representation and convergence thereof given initial bimodal excitation, assuming a Kerr-type nonlinear index and slowly varying approximations.3When we adopt the notation of Ref.3with difference between the effective indices of the two initially excited modesδneff,the Kerr coefficientn21,core half-widthρ, andPref=ρδneff/n2,I, forP/Pref<1, the two-mode representation is highly accurate for describing the nonlinear phase shifting and small nonlinear coupling. AsP/Pref≈ 1 is approached, the field evolution is well described in terms of 3 or 4 local modes. ForP/Pref≥2, "violent pulsations"2are observed, and the local-mode representation may not necessarily be uniformly convergent. These results may be compared with field evolution obtained by using the beam-propagation method.
To achieve high order accurate numerical approximation to nonlinear smooth functions, we employ and generalize the idea of double-logarithmic reconstruction for the numerical solution of hyperbolic equations. The result is a class of...
moreTo achieve high order accurate numerical approximation to nonlinear smooth functions, we employ and generalize the idea of double-logarithmic reconstruction for the numerical solution of hyperbolic equations. The result is a class of efficient third-order schemes with a compact stencil. These methods handle discontinuities as well as local extrema within the standard semi-discrete MUSCL algorithm using only a single limiter function.
This study reports the design and analysis of a plasmonic sensor based on a heavily doped silicon and metallic grating structure working in the mid-infrared region. The numerical results show that the reflection spectrum of the...
moreThis study reports the design and analysis of a plasmonic sensor based on a heavily doped silicon and metallic grating structure working in the mid-infrared region. The numerical results show that the reflection spectrum of the phosphorous-doped Si grating structure with a dopant concentration of 1 × 2020 has a sharp asymmetric Fano resonance dip, which is strongly dependent on the refractive index change in the surroundings. It yields a sensitivity of 8000 nm/RIU (refractive index unit) and 950 nm/RIU working in the air and water media, respectively, very high values compared with that of existing devices. Moreover, the Fano resonance caused by coupling of the Wood–Rayleigh anomaly and surface plasmon resonances is demonstrated by calculating the magnetic field and Poynting vector patterns. Further, a feasible and easy fabrication process of the sensor featuring high performance is represented.
People in the Middle East are facing the problem of freshwater shortages. This problem is more intense for a remote region, which has no access to the power grid. The use of seawater desalination technology integrated with the generated...
morePeople in the Middle East are facing the problem of freshwater shortages. This problem is more intense for a remote region, which has no access to the power grid. The use of seawater desalination technology integrated with the generated energy unit by renewable energy sources could help overcome this problem. In this study, we refer a seawater reverse osmosis desalination (SWROD) plant with a capacity of 1.5 m3/h used on Larak Island, Iran. Moreover, for producing fresh water and meet the load demand of the SWROD plant, three different stand‐alone hybrid renewable energy systems (SAHRES), namely wind turbine (WT)/photovoltaic (PV)/battery bank storage (BBS), PV/BBS, and WT/BBS are modeled and investigated. The optimization problem was coded in MATLAB software. Furthermore, the optimized results were obtained by the division algorithm (DA). The DA has been developed to solve the sizing problem of three SAHRES configurations by considering the object function's constraints. These results show that this improved algorithm has been simpler, more precise, faster, and more flexible than a genetic algorithm (GA) in solving problems. Moreover, the minimum total life cycle cost (TLCC = 243 763$), with minimum loss of power supply probability (LPSP = 0%) and maximum reliability, was related to the WT/PV/BBS configuration. WT/PV/BBS is also the best configuration to use less battery as a backup unit (69 units). The batteries in this configuration have a longer life cycle (maximum average of annual battery charge level) than two other configurations (93.86%). Moreover, the optimized results have shown that utilizing the configuration of WT/PV/BBS could lead to attaining a cost‐effective and green (without environmental pollution) SAHRES, with high reliability for remote areas, with appropriate potential of wind and solar irradiance.
A surface plasmon resonance (SPR) in terahertz range is demonstrated in InSb. Using an Otto configuration, the surface plasmon is excited on the interface between semiconductor and a thin polymer film by silicon prism. Due to the low...
moreA surface plasmon resonance (SPR) in terahertz range is demonstrated in InSb. Using an Otto configuration, the surface plasmon is excited on the interface between semiconductor and a thin polymer film by silicon prism. Due to the low effective mass of InSb it is possible to tune SPR by an external magnetic field in transversal configuration. It is possible to achieve resonance shift up to 100 GHz with magnetic field 0.25 T. The experimental results show good agreement with the theoretical model.
Numerical solutions are obtained for a novel inhomogeneous semiconductor hybrid plasmonic waveguide structure by using Finite Element Method (FEM) method (Comsol). The guiding properties of an inhomogeneous semiconductor hybrid surface...
moreNumerical solutions are obtained for a novel inhomogeneous semiconductor hybrid plasmonic waveguide structure by using Finite Element Method (FEM) method (Comsol). The guiding properties of an inhomogeneous semiconductor hybrid surface plasmon polaritons (ISHSPPs) slot waveguide was numerically analyzed at an optical frequency, which shows the ISHSPPs waveguide could surpass the diffraction limit while still maintaining long polariton's propagation lengths. The geometric dependence of the mode characteristics of the proposed structure is analyzed in detail, showing strong confinement with long propagation lengths. Numerical results offer a potential for use in several applications such as biosensors.
We report on a theoretical investigation of the dispersion relation of surface plasmon polaritons (SPPs) on a periodically corrugated semiconductor surface. We assumed Drude’s permittivity model of the semiconductor, which accurately...
moreWe report on a theoretical investigation of the dispersion relation of surface plasmon polaritons (SPPs) on a periodically corrugated semiconductor surface. We assumed Drude’s permittivity model of the semiconductor, which accurately describes the loss of these spoof SPPs. In the THz frequency range, the properties of the dispersion and loss of spoof SPPs on corrugated Si surfaces are studied. A low-loss propagation of spoof SPPs can be achieved by an optimum design of the surface structure. It was found that by increasing the lattice constant or by reducing the groove depth, the investigated structure can provide a low guiding attenuation.
Preliminary experimental results are reported on all-optical and electrooptical control of transfer of light energy in a GaAs-based multiple-quantum-well-coupled planar nonlinear directional coupler. It is believed that this is the first...
morePreliminary experimental results are reported on all-optical and electrooptical control of transfer of light energy in a GaAs-based multiple-quantum-well-coupled planar nonlinear directional coupler. It is believed that this is the first semi-conductor ΔK switch and the first report on results obtained near the exciton-resonance wavelength.
Transparent signal regeneration is of great interest for long-haul fiber optic communication systems, because it can eliminate the optical-electrical-optical signal conversions in optical repeaters and potentially has higher speed.
Optical pulse wave propagation in nonlinear and dispersive medium is simulated by constrained interpolated profile (CIP) method. In one dimensional space with dispersion and nonlinearity, Gaussian envelope pulse modulated by optical...
moreOptical pulse wave propagation in nonlinear and dispersive medium is simulated by constrained interpolated profile (CIP) method. In one dimensional space with dispersion and nonlinearity, Gaussian envelope pulse modulated by optical carrier wave propagates successfully with physically reliable manner for typical small and large amplitudes. The spreading and compressing behavior for small and large input amplitudes are caused by trade-off between linear dispersion and nonlinear refractive index modulation of the medium.
A novel plasmonic Mach-Zehnder interferometer (MZI) biosensor, which is based on a simple slit-groove microstructure, is reported in the terahertz (THz) regime. The permittivity-sensitive phase difference between the two propagating SPPs...
moreA novel plasmonic Mach-Zehnder interferometer (MZI) biosensor, which is based on a simple slit-groove microstructure, is reported in the terahertz (THz) regime. The permittivity-sensitive phase difference between the two propagating SPPs waves gives rise to the modulation of the transmitted intensity. The results show that the MZI biosensor possesses a sensitivity as high as 140000 nm/RIU (refractive index unit). The highly compact configuration may find important applications in areas of sensing and integrated THz circuits (ITCs).
The use of semiconductors in optics and photonics is notoriously broad. This paper explores the use of gratings on semiconductor plasmonic waveguides.
We consider the surface plasma polariton dispersion in inhomogeneous semiconductor/ air interface. The plasma permittivity in a two-layer compound is studied by inclusion of an inhomogeneous plasma density. Numerical solutions were...
moreWe consider the surface plasma polariton dispersion in inhomogeneous semiconductor/ air interface. The plasma permittivity in a two-layer compound is studied by inclusion of an inhomogeneous plasma density. Numerical solutions were obtained for the plasma dispersion curve of an inhomogeneous semiconductor/dielectric structure. A detailed analysis was carried out to derive an expression for the dispersion of a silicon/air interface, or other [1], by applying our new original approach [2]. This approach takes into account the free-charge carrier concentration profile effect.
This paper studies the photonic nanojets generated by micro-cylinders with rough surfaces using FDTD method. Photonic nanojets are observed when plane wave propagates through various micro-cylinders embedded in vacuum. When...
moreThis paper studies the photonic nanojets generated by micro-cylinders with rough surfaces using FDTD method. Photonic nanojets are observed when plane wave propagates through various micro-cylinders embedded in vacuum. When micro-cylinders are embedded in water medium, the dimension of the generated photonic nanojets increases, as well as the distance between the micro-cylinders and the photonic nanojets. While the maximum intensity of the photonic nanojets decreases. In addition, photonic nanojet disappears when using rough surface micro-cylinders due to the strong random scattering and interference effect. In practice, these results provide guidance when using photonic nanojets for probing and manipulating nanoscale objects, nanopatterning and nanolithography with subwavelength spatial resolution and ultra-high density optical storage.
Experimental results with a simple all-optical nonlinear directional coupler are reported. The element was fabricated by Molecular Beam Epitaxy (MBE) and is composed of two Al.18Ga.82As waveguides of 1.85-μm thickness, coupled through a...
moreExperimental results with a simple all-optical nonlinear directional coupler are reported. The element was fabricated by Molecular Beam Epitaxy (MBE) and is composed of two Al.18Ga.82As waveguides of 1.85-μm thickness, coupled through a 0.948-μm-thick MQW. The MQW consists of 30 periods of alternating 10.6-nm GaAs and 21-nm Al.33Ga.67As layers. The waveguides are planar without any lateral confinement. The whole structure was grown on a GaAs substrate and is buffered on both sides by a 2.05-μm-thick layer of Al.72Ga.28As composition. The structure is illustrated in Figure 1.
The plasmonic properties of semiconductors, transparent conductive oxides, transition metal nitrides, noble metals and aluminium are discussed in this article. It is shown that for each frequency in the wide range of 1 meV up to 15 eV the...
moreThe plasmonic properties of semiconductors, transparent conductive oxides, transition metal nitrides, noble metals and aluminium are discussed in this article. It is shown that for each frequency in the wide range of 1 meV up to 15 eV the material with appropriate plasmonic properties can be chosen. Special attention is devoted to the semiconductors due to their tunability, extremely low effective masses and exceptionally high carrier mobility that allows to creation of plasmonic structures operating in the terahertz region.Web of Science1687800779
This dissertation investigates interferometric optical Fourier processors for the purpose of computation. Both processors contain a conventional optical Fourier processor and employ a common-path type of interferometer to indirectly...
moreThis dissertation investigates interferometric optical Fourier processors for the purpose of computation. Both processors contain a conventional optical Fourier processor and employ a common-path type of interferometer to indirectly measure the complex-valued optical distribution produced in the back focal-plane of the Fourier transform lens. The first employs a point-diffraction interferometer while the second uses a novel interferometric technique. Both interferometric optical Fourier processors are demonstrated in a moving-object trajectory-estimation application.
This study focuses on the photonic nanojets generated by micro-cylinders with nanostructured surfaces using FDTD method. When micro-cylinders are embedded in different medium such as air or water, the dimension and maximum intensity of...
moreThis study focuses on the photonic nanojets generated by micro-cylinders with nanostructured surfaces using FDTD method. When micro-cylinders are embedded in different medium such as air or water, the dimension and maximum intensity of the generated photonic nanojets will change, as well as the distance between the micro-cylinders and the photonic nanojets. More importantly, photonic nanojet may disappear when a rough surface micro-cylinder is used due to the strong random scattering and interference effect. In practice, these numerical study results can provide guidance when using photonic nanojets for imaging nanoscale objects.
Magneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS) and the Fourier transform far-infrared spectroscopy (far-FTIR). A Huge...
moreMagneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS) and the Fourier transform far-infrared spectroscopy (far-FTIR). A Huge polar magneto-optical (MO) Kerr-effect (up to 20 degrees in rotation) and a simultaneous plasmonic behavior observed at low magnetic field (0.4 T) and room temperature are promising for terahertz nonreciprocal applications. We demonstrate the possibility of adjusting the the spectral rage with huge MO by increase in n-doping of InSb. Spectral response is modeled using generalized magneto-optical Drude-Lorentz theory, giving us precise values of free carrier mobility, density and effective mass consistent with electric Hall effect measurement.
Summary form only given. The nonlinear optical response of a material is relatively weak compared to the linear response, but nonlinear responses can be enhanced by increasing the power of the input frequencies to be mixed. Similarly,...
moreSummary form only given. The nonlinear optical response of a material is relatively weak compared to the linear response, but nonlinear responses can be enhanced by increasing the power of the input frequencies to be mixed. Similarly, conversion efficiency can be enhanced by increasing the interaction volume of the structure. Phase-matching, which is a momentum conservation, is important for increasing the energy exchange between the waves. Fulfilling the phase-matching along the direction of the propagating waves will increase the power of the resulting wave of the mixing. GaAs is a cubic structure lattice which has isotropic optical properties. Because it is not possible to achieve birefringence phase-matching using GaAs, an artificial birefringence medium is made using other layers of different materials to obtain the phase-matching. Quasi-phase-matching is also possible by modulating the second-order susceptibility χ(2) along the direction of the propagation to form grating. The two major techniques are domain-reversal quasi-phase-matching and domain-disordered quasi-phase-matching. This study focuses on frequency down-conversion in the mid-infrared range. Frequency down-conversion is an essential technique for generating mid-infrared optical frequencies when it is not possible to generate them by conventional sources. We study phase-matching using effective permittivity by inclusions of negative permittivity materials into GaAs, and investigate materials such as metals or doped GaAs. Gold is selected to be the inclusion material into GaAs as a host medium. Using the Maxwell-Garnett model of effective permittivity theories, we form the desired effective permittivity to obtain phase-matching. A one-dimensional optical antenna array is selected for the inclusions. By changing the inclusion volume fraction and depolarization factor of cylindrical optical antennas, we can specify effective permittivity in a certain direction. To simplify the analytical analysis of the problem, we assume the depression relations of the propagated waves in a bulk medium of GaAs. Omitting the power calculations, we achieve phase-matching for certain wavelengths, depending on the volume inclusions and deportation factors of the antennas rods. This result promises that phase-matching is possible in channel waveguides.