We demonstrate many novel photo-conductive antenna (PCA) designs, capable of emitting Terahertz radiation with high average power. For this, bulk substrate, electrode geometry and design, Focusing of the incident radiation, array of electrodes, electrode structure and area between the two electrodes can be modified. Some of the designs show enhanced bandwidth of the emitted THz radiation pulse. For Example, one such device consists of Au electrodes on a semi-insulating GaAs substrate. A Photonic Crystal like plasmonic nano-structure array is embedded in the substrate between the two electrodes. This array shows plasmonic enhancement of the 800 nm IR light near the nano-structures enhancing THz radiation emission. Secondly, the nano-structures act as defect sites which enables fast carrier capture, enhancing THz bandwidths. At the same time, the terminal currents are highly reduced implying robustness of the device to high applied bias voltages. THz spectroscopy is useful in material studies as well. Resonant transmission of electromagnetic radiation through an array of rectangular apertures occurs when electric field vectors of the incident wave are perpendicular to the long axis of the aperture. We study several designs of Metmaterials. Here we will mention about periodic array of asymmetric aperture and demonstrate that introducing a taper along long axis can yield transmission for both orthogonal polarizations. We present several studies of different Metamaterial designs and describe some interesting results obtained using external perturbations on these Metamaterial substrates. References: [1.] A. Bhattacharya; D. Ghindani and S. S. Prabhu, ``Enhanced terahertz emission bandwidth from photoconductive antenna by manipulating carrier dynamics of semiconducting substrate with embedded plasmonic metasurface", Optics Express, 27, 30272 (2019). [2.] Arnab Pattanayak, Goutam Rana, Ravikumar Jain, Arkabrata Bhattacharya, Siddhartha P. Duttagupta, Prasanna S. Gandhi, Venu Gopal Achanta, and S. S. Prabhu, “Near-unity THz transmission through asymmetric aperture array with polarization controlled resonant peaks and Q-factors”, Accepted in Journal of Applied Physics 2020.
PhD in Physics from TIFR. Currently Associate Professor of Physics. He has more than 52 papers in international journals, and several articles (popular and technical) in many magazines and more than ~80 papers in conferences and has given several invited talks. Research Interests are Ultrafast Time resolved Phenomena in Materials, THz Spectroscopy of Materials, Metamaterials, High field THz and Near Field THz Microscopy