25 February 2016 Sub-wavelength nano-electrode structures to improve the performance of terahertz photomixers
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By utilizing the sub-wavelength metallic structures in the active region of the photomixer, the confinement and concentration of electric field from optical pump lasers on a photoconductive substrate can be efficiently achieved as these sub-wavelength metallic structures are exhibiting the nano-antenna effect over a high index photoconductive substrate. Designing the sub-wavelength metallic structures, branch-like nano-electrodes structures, a new strategy to improve carrier capture was developed in which more carrier collection points occupy across the area of the pumping laser source. These branch-like nano-electrode structures were found to improve THz emission intensity of a photomixer by approximately one order of magnitude and optical-to-THz conversion efficiency by 10 times higher than that of photomixer with one row of nano-electrodes separated by the same 100nm gap. The enhancement is attributed to a more efficient collection of generated carriers due to a more intense electric field under the branch-like nano-electrodes structures. This is coupled with increased effective areas where strong tip-to-tip THz field enhancements were observed. The more efficient THz photomixer will greatly benefit the development of continuous wave THz imaging and spectroscopy system.
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Qing Yang Steve Wu, Qing Yang Steve Wu, Hendrix Tanoto, Hendrix Tanoto, Ding Lu, Ding Lu, Chan Choy Chum, Chan Choy Chum, Mei Sun, Mei Sun, Zhi Ning Chen, Zhi Ning Chen, Soo Jin Chua, Soo Jin Chua, Jinghua Teng, Jinghua Teng, } "Sub-wavelength nano-electrode structures to improve the performance of terahertz photomixers", Proc. SPIE 9747, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications IX, 974703 (25 February 2016); doi: 10.1117/12.2202416; https://doi.org/10.1117/12.2202416


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