Publication

Abstract : This article reports an in-depth study of interdigitated photoconductive antenna (IPCA) structures for broadband, high electric field, efficient terahertz (THz) generation and detection. The photoconductive antenna (PCA) is the key component which can be used as both the emitter and detector in the THz-time domain spectroscopy for imaging application. The proposed IPCA can easily overcome the limitations of conventional dipole or bow-tie PCA, like, less bandwidth, low optical-to-THz conversion efficiency and less radiated THz power. In this work, the performance of IPCAs, which is made of silver interdigitated electrodes and thin layer of low-temperature-grown GaAs (LTG-GaAs) on top of semi-insulating GaAs (SI-GaAs) substrate, has been studied by varying the geometry of the interdigitated elements until it reaches to the plasmonic limit. Several time- and frequency-dependent parameters, such as carrier density, conductance, impedance, photocurrent, bandwidth, optical-to-THz efficiency, THz radiated power, have been investigated thoroughly depending on the input ultrafast laser parameters, temperature-dependent mobility of photo-carriers and the dimension of the IPCAs. The Scharfetter and Gummel’s drift-diffusion model has been used to calculate the photo-carrier density while focuses the laser pulses at the gap of IPCA structures. The optimum results have been found in terms of single-cycle THz pulses of 0.3 ps, bandwidth of ∼ 13.8 THz, optical-to-THz efficiency of 0.1265% and average radiated power of 3.9564 mW for the 20-nm interdigitated electrode (teeth) width, i.e. 44 elements IPCA. The results of different dimensions of IPCAs have been compared among them and with the published conventional PCAs. These IPCAs will be very useful for future generation THz-transceiver systems.