International Conference on Energy, Communication, Data Analysis & Soft Computing, SKR Engineering College, Chennai,  1.8.2017; Cochin University of Science & Technology, Cochin, 7.9.2016;  Engg. Design Department, IIT, Chennai, 29.10.2015.

The spectrum between 300 MHz to 30 GHz is referred to as the microwave band; 30 GHz and 300 GHz is referred to as the mm-wave band, and the 300 GHz to 3000 GHz band is called by electronics engineers as sub-mm-wave and by the optics engineers as Thz band. Starting from the radio, microwave oven and satellite and imaging applications all depend on this spectrum of frequencies. Though it was thought that due to the emergence of GaN, vacuum tubes would lose its battle to solid-state devices, vacuum technology has continued to evolve, as they serve as powerful sources of radiation. This is because a single device power of VED, exceed those of solid-state devices by such large margins, up to THz as the electron beam flows without any collision in a vacuum device. Some of the vacuum electron devices are Magnetron, Klystron and TWTs and new generation devices like Gyrotron, FEL, MILO, EIO, and EIKs. Despite many valuable, useful applications, the adoption of terahertz waves has been slow because of the limited output power available from current sources like HEMT, optically pumped lasers, Gunn and IMPATT diodes. Gyrotrons, Backward wave oscillator are some of the technologies that are currently in the process of bridging this gap. Micro-EDM and Si DRIE and LIGA technologies offer the best prospects for THz-regime Vacuum Electronic Device fabrication.