Abstract

The development of Terahertz Photoconductive Antennas (THz PCAs) with compact size, room-temperature operation, broadband spectral response, and reasonably low cost has significantly contributed to the growing popularity of THz research since the early 2000s. However, the main challenge restricting the applications of THz technology largely to laboratory environments is the very low power output, which arises from the intrinsically poor efficiency of THz photoconductive antennas. This low efficiency originates from several factors, most notably the optical-to-THz conversion process, which is strongly influenced by the high refractive index of III–V direct bandgap semiconductors (e.g., LT-GaAs, InGaAs, InP), despite their ultrafast carrier velocities and extremely short recombination times (sub-picosecond for broadband radiation). To improve coupling of the femtosecond optical pump beam, various approaches have been explored, such as anti-reflection coatings, plasmonic electrodes, and plasmonic nanoantenna. Each of these techniques, however, has inherent limitations: anti-reflection coatings are highly wavelength-sensitive and suffer from carrier screening beyond certain pump powers, while plasmonic structures are subject to reflection and ohmic losses. In contrast, photonic crystal structures integrated on the surface of THz PCAs offer multiple advantages. With appropriate geometries, they can minimize reflection losses, avoid ohmic dissipation, and, through engineered defects in the photocarrier pathways, help suppress carrier screening. By optimizing the geometry of such structures, maximum confinement of the pump light can be achieved, thereby enhancing the photogenerated carriers and improving overall THz generation efficiency.

Biography

Goutam Rana is affiliated with SRM Institute of Science and Technology, India. His academic work focuses on research, education, and innovation, contributing to scientific advancement and academic development in his field of study.