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1. Investigation of Photoconductive Antenna Electrodes on Terahertz Signal Generation

   Santos, J. (January 2021, IEEE Antennas and Propagation Symposium)

   null (Ed.)

   This paper presents an investigation of terahertz (THz) signals generated using photoconductive antennas (PCAs) based on different electrode geometries. The geometry of the electrodes influences the shape of the THz pulse and its frequency spectrum. The geometry can be used to provide improvements to the bandwidth of the PCA. We used the transient solution of the RF module of COMSOL Multiphysics to simulate the radiated electric field based on using the photoconductive current as a time domain source in the gap of the antenna. The dimensions of a previously published bowtie H-dipole antenna were used as reference that was modified to three new configurations. The results show that the bowtie-H-dipole antenna provided broader bandwidth compared with the fractal, slot, and/or circular shape electrodes PCAs. 

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2. Investigation of Photoconductive Antenna Electrodes on Terahertz Signal Generation

   Santos, j; El-Shenawee, M. (December 2021, IEEE Antennas and Propagation Symposium)

   null (Ed.)

   This paper presents an investigation of terahertz (THz) signals generated using photoconductive antennas (PCAs) based on different electrode geometries. The geometry of the electrodes influences the shape of the THz pulse and its frequency spectrum. The geometry can be used to provide improvements to the bandwidth of the PCA. We used the transient solution of the RF module of COMSOL Multiphysics to simulate the radiated electric field based on using the photoconductive current as a time domain source in the gap of the antenna. The dimensions of a previously published bowtie H-dipole antenna were used as reference that was modified to three new configurations. The results show that the bowtie-H-dipole antenna provided broader bandwidth compared with the fractal, slot, and/or circular shape electrodes PCAs. 

   more » « less
3. Investigation of Photoconductive Antenna Electrodes on Terahertz Signal Generation

   Santos, J; El-Shenawee, M. (December 2021, IEEE Antennas and Propagation Symposium)

   This paper presents an investigation of terahertz (THz) signals generated using photoconductive antennas (PCAs) based on different electrode geometries. The geometry of the electrodes influences the shape of the THz pulse and its frequency spectrum. The geometry can be used to provide improvements to the bandwidth of the PCA. We used the transient solution of the RF module of COMSOL Multiphysics to simulate the radiated electric field based on using the photoconductive current as a time domain source in the gap of the antenna. The dimensions of a previously published bowtie H-dipole antenna were used as reference that was modified to three new configurations. The results show that the bowtie-H-dipole antenna provided broader bandwidth compared with the fractal, slot, and/or circular shape electrodes PCAs. 

   more » « less
4. Fabrication and Measurement of LT-GaAs Photoconductive THz Broadband Antennas

   Zachary P. Uttley and Magda O. El-Shenawee (July 2022, Digest IEEE Antennas and Propagation Society International Symposium)

   IEEE (Ed.)

   This paper presents fabrication and experimental measurements of broadband terahertz (THz) photoconductive antennas (PCAs), based on the conventional low temperature gallium arsenide (LT-GaAs) material. Various antenna electrode geometries, that were previously designed through computer simulations, are fabricated using the electron beam lithography (EBL). The generated time domain pulse is measured using a time domain spectroscopy system (TDS). The bandwidth of each emitting device is obtained using the fast Fourier transform of the generated electric field pulse. 

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5. Experimental and Computational Analysis of Broadband THz Photoconductive Antennas

   https://doi.org/10.1155/2023/6682627  

   Uttley, Zachary; Santos Batista, Jose; Pirzada, Bilal; El-Shenawee, Magda (February 2023, International Journal of Antennas and Propagation)

   Gennarelli, Claudio (Ed.)

   The work presents the fabrication and measurements of four LT-GaAs photoconductive terahertz (THz) antennas with different geometries of metallic electrodes. The goal is to analyze the overall bandwidth of the antennas through a comparison between the spectra of the generated photocurrent in the antenna gap, the radiated electric field THz pulse, and the S11 parameter of the metallic electrodes. The photocurrent density and the S11 parameters are computed using COMSOL multiphysics, while the generated THz pulse was experimentally measured using a time-domain spectroscopy system. The polarizations of the photoconductive antennas are experimentally measured, using x-cut quartz crystal halfwave plates, showing polarization in the direction of the electrode’s long axis. Pinholes are used to verify system alignment and quality of the radiated signal spectra. The results show that the spectra of the radiated THz pulses in all four antennas considered in this work are dominated by the behavior of the S11 parameter at the lower part of the frequency band, but with the decreasing photocurrent dominating the spectra at higher frequencies. 

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