This proposal focuses on the development of an application-specific component that works in the Terahertz (THz) regime; in this context, we propose to realize a THz source with innovative features specific for monitoring systems for safety and security. Until now the use of THz monitoring system has been strongly limited due to the very low power and the large dimensions of the existing sources in the THz.The OPTHER project aims at solving this limitation with a breakthrough with respect to all the other solutions up to know available in Europe, U.S. and Asia. We plan to use available optical THz sources (such as Quantum Cascade Lasers (QCL) or photomixing systems) and boost their performances by designing and fabricating compact, efficient and reliable novel vacuum THz amplifier.The breakthrough of this proposal is the enhancement of the performance of THz optical source by using vacuum THz amplifiers purposely designed and integrated with the optical driver. The novel THz amplifier will be based on field emitting carbon nanotubes (CNT) used as cold cathodes. Two alternative schemes will be employed for amplification.- In the first one (THz drive signal amplifier) the continuous wave electron beam emitted by the CNT cathode is modulated by the electric field in the interaction structure driven by a THz signal- In the second one (optically modulated beam THz amplifier) the emission of current is driven by the THz signal. With this second scheme the delivery of high power output should be facilitated.The source output signal will be fully characterized using commercial broadband detectors such as Schottky diodes or bolometers. The composition of the consortium has been carefully arranged for including all the expertise necessary for a successful conclusion of the research activity. In fact, the present consortium is composed by 6 partners, with complementary research expertise and background: two universities, a research institute and three industries