In this paper we apply the terahertz time-domain spectroscopy (THz-TDS) to obtain optical functio... more In this paper we apply the terahertz time-domain spectroscopy (THz-TDS) to obtain optical function spectra in the range from 0.06 to 3 THz. Polarization sensitivity is obtained using azimuth-controlled wire-grid polarizers. We demonstrate general methods on characterization of plasmonic semiconductors. Detail characterization of optical and magneto-optical material properties is also motivated by a need of optical isolator in THz spectral range. The technique is applied to III-V semiconductors. The typical material is a single crystal undoped InSb having the plasma frequency in the range of interest. With appropriate magnetic field (in our case 0.4 T) we observed coupling of plasma and cyclotron behavior of free electrons with gigantic magneto-optic effect in the THz spectral range.
Nonlinear optical effects based on the χ 2 nonlinearity (optical second harmonic generation, opti... more Nonlinear optical effects based on the χ 2 nonlinearity (optical second harmonic generation, optical frequency mixing, parametric amplification and generation) in optical waveguides have been intensively studied from the very beginning of integrated optics1–3 There were hopes that light confinement for relatively long distances in waveguides would help significantly reduce light power required for efficient nonlinear interaction. Materials fdr guided-wave optical nonlinear applications have to fulfil a number of requirements simultaneously: they should not only exhibit large nonlinearity but it must also be suitable for fabricating high-quality optical waveguides. Moreover, there must exist a way to fulfil the phase matching condition, and, last but not least, the mode field overlap of all three interacting modes has to be as high as possible for good efficiency of the nonlinear process. From just a few suitable materials, lithium niobate crystal is still one of the most promising choices.
Third-order nonlinearities in optical waveguides have received considerable recent attention,1wit... more 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 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 a... more 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 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... more 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 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.
International Journal of Energy Research, Jul 13, 2020
People in the Middle East are facing the problem of freshwater shortages. This problem is more in... more 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 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 confi... more 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 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.
In this paper we apply the terahertz time-domain spectroscopy (THz-TDS) to obtain optical functio... more In this paper we apply the terahertz time-domain spectroscopy (THz-TDS) to obtain optical function spectra in the range from 0.06 to 3 THz. Polarization sensitivity is obtained using azimuth-controlled wire-grid polarizers. We demonstrate general methods on characterization of plasmonic semiconductors. Detail characterization of optical and magneto-optical material properties is also motivated by a need of optical isolator in THz spectral range. The technique is applied to III-V semiconductors. The typical material is a single crystal undoped InSb having the plasma frequency in the range of interest. With appropriate magnetic field (in our case 0.4 T) we observed coupling of plasma and cyclotron behavior of free electrons with gigantic magneto-optic effect in the THz spectral range.
Nonlinear optical effects based on the χ 2 nonlinearity (optical second harmonic generation, opti... more Nonlinear optical effects based on the χ 2 nonlinearity (optical second harmonic generation, optical frequency mixing, parametric amplification and generation) in optical waveguides have been intensively studied from the very beginning of integrated optics1–3 There were hopes that light confinement for relatively long distances in waveguides would help significantly reduce light power required for efficient nonlinear interaction. Materials fdr guided-wave optical nonlinear applications have to fulfil a number of requirements simultaneously: they should not only exhibit large nonlinearity but it must also be suitable for fabricating high-quality optical waveguides. Moreover, there must exist a way to fulfil the phase matching condition, and, last but not least, the mode field overlap of all three interacting modes has to be as high as possible for good efficiency of the nonlinear process. From just a few suitable materials, lithium niobate crystal is still one of the most promising choices.
Third-order nonlinearities in optical waveguides have received considerable recent attention,1wit... more 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 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 a... more 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 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... more 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 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.
International Journal of Energy Research, Jul 13, 2020
People in the Middle East are facing the problem of freshwater shortages. This problem is more in... more 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 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 confi... more 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 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.
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Papers by Michael Cada