TeraHertz: Quasi-optics or Submillimeter Waves? History, Actual Limits and Future Developments for Security Systems

The risk of mass murder due to terroristic attacks is more and more a very dangerous problem to be countered for security in civil and military world. One the most appealing technologies recently emerging is based on THz detection of explosives and other forms of threats, although, up to now, problems in operational devices (both for sensors and sources) are strongly limiting the application of this technology especially considering size, complexity in its use, and overall the cost and the need of low temperature for sensors. A Review Paper on THz most advanced Sensors and Sources Technologies is presented especially for Security Systems applications, possibly in unattended devices at room temperature. Keeping the Rule that “Future is depending from Present and Present has been originated by Past” the history of terahertz science, for learning by historical lessons, is presented and discussed identifying winning solutions and disappointing delusions either technological and/or operational. A Review what terahertz waves are, how they are generated, transmitted and detected and an evaluation for a common technological culture and discussion about what can be expected for the future developments, is outlined.