In recent years, a number of terahertz (THz) full body scanners have been deployed at the airports and other security checkpoints around the world. According to this 2013 news report, the New York Police Department (NYPD) have started testing a new remote terahertz camera detection system which can detect firearms concealed beneath layers of clothing. Apart from the ethical and unknown health risk issues raised by the use of terahertz body scanners in public places, the question is how technically feasible it is to make these systems compact and portable so that they can be packed into handheld devices. The current terahertz passive imagers that do not expose the object under investigation to terahertz radiation use bulky and expensive cryogenic coolers to reduce their sensors’ thermal noise. A potentially compact and handheld terahertz imager that works at room temperature need to illuminate the object under investigation by terahertz radiation, making the device even more controversial. According to several news reports, full body scanners that expose people to electromagnetic radiations are being removed from airports.