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Tunable Terahertz Graphene-Based Absorber Design Method Based on a Circuit Model Approach
摘要： In this paper, a simple, fast, and novel method for designing a tunable terahertz absorber with arbitrary central frequency and desired fractional bandwidth is presented. The proposed absorber consists of a single layer periodic array of graphene ribbons (PAGRs), placed a quarter wavelength from a metallic ground, separated by a dielectric material. An analytical circuit model of the terahertz absorber is used to obtain analytical expressions for the input impedance of the proposed device. Then, a simple expression for determining the value of capacitance and the resonance conditions of the RLC circuit is used to achieve a terahertz absorber with arbitrary central frequency and desired fractional bandwidth. The proposed method is applicable for the design of both narrowband and broadband absorbers, with only one layer of graphene ribbons. Also, the presented method is applicable for designing ultra-wideband absorbers using multiple layered PAGRs. Full-wave numerical simulation is performed to verify the accuracy and validity of the presented method. Excellent performance of the proposed method in terms of computation time and memory resource and providing the desired terahertz absorber characteristics shows that our method is promising as a design approach for sensing, imaging and ?ltering applications.
关键词： circuit model,graphene,Terahertz absorber,transmission line method,tunable bandwidth
更新于2025-09-23 15:21:01
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Compact and low-power all-optical surface plasmon switches with isolated pump and data waveguides and a rectangular cavity containing nano-silver strips
摘要： In this paper, a plasmonic all-optical switch based on a novel topology is presented. The structure is composed of a rectangular cavity coupled with two cross waveguides. Several silver strips with a tapered pattern are inserted in the rectangular cavity to create a sharp edge in the transmission spectrum of the data signal. The cavity and waveguides are filled with a non-linear insulator with high Kerr-type nonlinearity. The vertical and horizontal waveguides are used for passing the data and pump signals, respectively. When in addition to the data signal, the pump signal is also applied, the refractive index of the Kerr material changes, which triggers the switching mechanism. Allocating two different paths for the data and pump signals results in a desirable isolation between these signals. The proposed switch is numerically simulated using finite difference time domain (FDTD) method. In order to verify the FDTD simulation results, the basic switch structure is also analyzed using the transmission line method. Compact size (considering two different input ports), low pumping intensity, simplicity, symmetrical structure, suitable isolation and high contrast ratios are the marked characteristics of the proposed all-optical switch. As a result, such a structure has the potential to be used in complex integrated optical circuits.
关键词： Surface plasmon polaritons,Transmission line method,Metal-insulator-metal waveguide,All-optical switch,Kerr effect,Metal strips
更新于2025-09-23 15:19:57
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A novel analytical method for designing a multi-band, polarization-insensitive and wide angle graphene-based THz absorber
摘要： In this paper, we propose a simple and analytical method to design a multi-band tunable graphene-based absorber using circuit model. The presented paper provides a flowchart and equations to design a multi-band absorber which tremendously simplifies the design procedure of a multi-band absorber. This paper only investigates the disk shape graphene-based absorber, but we believe the proposed method is extendable to all presented shapes of graphene which previously designers provided with a circuit model. To verify the accuracy of the presented method; we have designed several multi-band absorbers and used Full-wave numerical modeling of the structure to approve our method. Also, this paper studies the reliability of our proposed model by investigating the fabrication sensitivity of the structure. Lastly, this paper investigates to see how a multi-band absorption spectra behave, in case there are any errors during the fabrication phase. The designed absorbers have potential applications in various fields of active THz metamaterials, tunable filters, and sensors. The graphene-based disk-shaped absorber has the advantage of polarization insensitivity, wide-angle absorption and ease of implementation due to its simple shape. Another advantage of using graphene in the absorber structure is that with the availability of changing the Fermi energy level, it is possible to tune the absorption frequency of the multi-band absorbers.
关键词： Circuit model,Absorber,Graphene Terahertz,Tunable bandwidth,Transmission line method
更新于2025-09-19 17:15:36
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Nondestructive Contact Resistivity Measurements on Solar Cells Using the Circular Transmission Line Method
摘要： The contact resistivity (ρc) of screen-printed contacts is a significant component of series resistance in industrial solar cells. Measuring ρc with standard techniques, such as the transmission line method (TLM), requires that the custom printed test structures be isolated from the device. In this article, we present a method for measuring ρc on solar cells using the circular TLM (cTLM), where the test structures are hidden within the busbars of the solar cell. This alleviates the need for the test structure to be isolated from the device, allowing for the fast and nondestructive measurement of ρc without causing additional shading on the cell. These measurements are performed with a semiautomatic tool, the ContactSpot-PRO, used for the accurate and systematic measurement of the ρc on the cTLM structures. Our results show that the cTLM technique compares well to the linear TLM technique on several samples fired through a range of temperatures. However, numerical models generated using Quokka3 and scanning electron microscopy images indicate that structural differences in screen-printed TLM and cTLM structures affect the actual contact resistivity of each pattern. The numerical models also show how nonuniform sheet resistance beneath and in-between the printed contacts can affect the measured ρc when using both the TLM and cTLM.
关键词： screen-printed contacts,circular transmission line method,nondestructive measurement,contact resistivity,solar cells
更新于2025-09-11 14:15:04