225 Int. Journ. of Laser Science, Vol. 1, pp. 225–252 Reprints available directly from the publisher. Photocopying permitted by license only. © 2019 OCP Materials Science and Engineering Published by license under the OCP Science imprint, Old City Publishing, Inc. Design of an Optical Terahertz Generator N. KHAN 1,2, *, A. VICKERS 2 , N. ABAS 3 AND A.R. KALAIR 1 1 Department of Electrical Engineering, COMSATS Institute of Information Technology, Park Road, Islamabad 45550, Pakistan 2 School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, UK 3 Department of Electrical Engineering, University of Gujrat, Jalapur Jattan Road, Gujrat 50700, Pakistan. Detection of an improvised explosive device (IED) is a significant chal- lenge for security agencies. Last ditch strategy in dealing with terrorists is to maintain an upper edge over crime science in the market. Security officials use dogs, metal detectors, and scanners to sniff out chemical signatures. IED detection devices are available yet 17,000 to 20,000 civilians succumb to death every year. Detection devices and imaging scanners locate buried landmines and concealed weapons at check- points but are unable to recognize the suicide bombers in large crowds. Man is an intelligent machine who changes defence strategies with time depending on the feedback of sensing organs. Detection of an adaptive suicide bomber in crowded public places, or car bombs on busy roads in large cities, is still a big challenge requiring innovative research. Haz- ardous materials (HAZMAT) and metal detectors often fail to recognize high energy materials (HEM) based home-made explosives (HME) wrapped in plastics. Standoff lasers identify HAZMAT by decoding the vapour spectroscopic signatures at 1 m to 1 km distances but, fail to scan the concealed IEDs. The terahertz band (100 GHz to 10 THz, cor- responding to the 1 mm to 30.0 mm wavelengths) falls between the high microwave (1 mm to 30 mm) and the low infrared (IR) (0.7 to 30.0 mm) bands. Terahertz photons are reflected off mirrors like light, penetrate tarps like X-rays and are detected by dipole antennas like microwaves. Terahertz waves can readout concealed IED due to their penetrating yet non-ionizing properties. Dogs and robot borne detectors recognize explosives by a physical approach to the site, but spectroscopic and imaging devices from the remote. Lasers facilitate standoff detection of landmines and X-ray scanners, image vehicles, but terahertz are used to scan drivers. Quantum cascade laser (QCL), dipole antennas, time mul- tiplexed laser pulses, impact avalanche ionisation transit time (IMPATT) *Corresponding author: E-mail: nasrullahk@comsats.edu.pk