Terahertz (THz) waves have been used in many applications including homeland security screening, healthcare and environmental sensing. One of the key components for such high performance terahertz systems is the THz source. Generation of THz waves by optical excitation with a biased planar antenna on the photoconductive material, known as photomixing, is one of the most promising techniques to realize a continuously tunable, room-temperature operated, high spectral resolution and relatively compact THz source. The low efficiency of optical to terahertz conversion has so far limited the output power of CW THz photomixers to the microwatt level especially at 1THz and above. This low efficiency and low output intensity translate to low performance CW THz system and thus the development of highly efficient THz photomixers is highly desirable to improve the performance and thus the wide usability of THz system.
Deep sub-wavelength metallic structures have been used in microwave, terahertz and infrared regions to manipulate the electromagnetic waves. These metallic structures in the form of apertures can focus the electric field and generate intense localized electric field. By employing the deep sub-wavelength metallic structures in the active region of the photomixer, the confinement and concentration of electric fields from optical pump lasers on a photoconductive substrate can be efficiently achieved as these deep sub-wavelength metallic structures exhibit the nano-antenna effect, i.e., creating local intense electric field over a high index photoconductive substrate. Additionally, these deep sub-wavelength metallic structures in the forms of one-dimensional gratings and two-dimensional square meshes provide perfect anti-reflection property in the THz range by impedance matching phenomenon.
The main goal of this research is to study the effect of deep-sub wavelength structures in improving THz power generation and reducing the transmission loss using anti-reflection coating to enhance the performance of passive terahertz components. (Abstract shortened by UMI.)
|School:||National University of Singapore (Singapore)|
|Department:||Electrical and computer Engineering|
|School Location:||Republic of Singapore|
|Source:||DAI-B 77/06(E), Dissertation Abstracts International|
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