الفهرس 
Full Wave-Hydrodynamic FDTD Solver For A Novel Double Grating THz Detector
Summaryيوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
In the recent years, there is an increasing need for the terahertz (THz) communications, and the THz detectors for security and medical applications. Yet, the design and fabrication of the THz devices is very challenging due to the THz gap.
The THz gap is the frequency band located between the frequency band of the electronic devices and the frequency band of the photonic devices. The THz gap can be closed using the surface plasmons (SPs) approach. Unfortunately, the minimum operating frequencies for the SPs propagate at the metal-dielectric interface are located in the infrared frequency band. This issue can be solved by considering the propagation of the SPs inside the two dimensional electron gas (2DEG) layer. The 2DEG layer can be found in semiconductors hetero-structures or gated graphene structures. This approach is called the THz plasma wave electronics (THz plasmonics).
In this thesis, a novel 2D asymmetric double grating gate plasmonic THz detector is introduced. Distinct from the previously published 1D THz detectors, in which the responsivity is maximum in the direction normal to the grating, and vanishes in the direction parallel to the grating. The responsivity of the introduced 2D THz detector does not vanish in any direction. Thus, the introduced THz detector is appropriate for detecting incident THz signals with different polarizations.
The modeling of the introduced 2D THz detector with high accuracy is also a challenging operation. The modeling can be done with several techniques. The first technique is to model the THz detector using the electronic model only. This model does not give any information about the electric or magnetic fields inside the device.
The second technique is to model the THz detector using the electronic model and the electrostatic (Poisson) model. This model accuracy is higher than the previous one, as it gives information about the quasi-static electric field inside the device. Yet, this technique does not give any information about the magnetic field inside the device.
The third technique is to model the device using both the electronic model and the electromagnetic model. This is achieved by solving Maxwell’s equations and the hydrodynamic equations simultaneously. Unfortunately, the analytic solutions are only available for the canonical problems with several assumptions. Thus, in this thesis a numerical method will be used to solve both Maxwell’s equations and the hydrodynamic equations simultaneously. As the main goal of this thesis is to calculate the responsivity frequency response of the introduced 2D THz detector in a frequency band, also since both the Maxwell’s equations and the hydrodynamic equations are time domain equations. Hence, the finite difference time domain (FDTD) method is the best candidate to achieve the goal.
The FDTD is first used to solve Maxwell’s equations separately. Then the developed full wave FDTD solver is verified using the analytic formulas. After that the hydrodynamic equations are approximated by the Drude surface conductivity. The Drude surface conductivity is implemented in the FDTD method using the surface boundary approach. Again the developed FDTD solver is verified using the analytic formulas. Finally the hydrodynamic equations are solved using the FDTD simultaneously with the Maxwell’s equations. The combined solver is called the full wave-hydrodynamic solver. The full wave-hydrodynamic solver is also verified. This time there is no accurate analytic formulas. So, the verifications will be with the aid of the experimental measurements, the surface boundary approach or prior published numerical solvers.