Abstract: This paper describes the status of the OPTHER (OPtically driven TeraHertz AmplifiERs) project and progress toward the THz amplifier realization. This project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the leading scientific and industrial European organizations working with vacuum electronics. Keywords: Vacuum amplifier, THz, travelling wave tube, carbon nanotube (CNT), electron gun. Introduction The OPTHER (OPtically driven TeraHertz amplifiERs) project represents a strenuous effort in terms of technological development, THz device design and integration towards development of a miniaturised THz amplifier based on travelling wave tube principles. The amplifier specifications in the OPTHER project are: - Operating frequency in the range from 0.3 THz to 2 THz. - Gain: 10 dB to 20 dB. - Output power > 10 mW (10 dBm). The operating frequency of 1 THz and 1 % bandwidth has been chosen for the proof of concept device realization. The preliminary analysis has demonstrated the feasibility of these specifications, which could be achieved by using a proper device configuration and employing carefully optimized components for the amplifier. Two amplification schemes are currently under development: - THz Drive Signal Amplifier. - Optically Modulated Beam THz Amplifier. In the first approach, the amplifier is designed to operate as a traveling wave tube in the backward wave mode. A novel slow-wave structure (SWS) has been designed to provide the required level of the beam-to-THz-wave interaction. The input port is placed at the collector end, while the output port is placed at the electron gun end. In an innovative approach (Optically Modulated Beam THz Amplifier), the pre-modulation of the e-beam is performed by direct illumination of a carbon nanotube cold cathode. The illumination of the carbon nanotubes is performed by a signal source, such as a dual frequency (THz spaced) laser or THz modulated laser. As a pre- modulated electron beam triggers the amplification process, a much shorter slow-wave structure can be used, allowing for more relaxed requirements to the focusing magnet in comparison to the conventional TWT circuit. CNT Cold Cathode and Microgun A CNT based cold cathode is a promising technology for the electron beam generation, which provides compact size, fast switching and avoids heating elements. A specific technological process has been developed ensuring stabilized and optimized growth conditions for vertically-aligned CNTs using several CVD techniques, for both single wall and multi wall CNTs on patterned substrates. A growth of individual CNTs of nm-scale 5.1: The OPTHER Project: Progress toward the THz Amplifier C. Paoloni 1 , F. Brunetti 1 , A. Di Carlo* 1 , M. Mineo 1 , E. Tamburri 1 , M.L. Terranova 1 , G. Ulisse 1 , A. Durand 2 , R. Marchesin 2 , K. Pham 2 , V. Krozer 3 , M. Kotiranta 3 , A. de Rossi 4 , D. Dolfi 4 , P. Guiset 4 , P. Legagneux 4 , J.P. Schnell 4 , A. Fiorello 5 , M. Dispenza 5 , A. Secchi 5 , V. Zhurbenko 6 , S. Megtert 7 , F. Bouamrane 7 , C.-S. Cojocaru 8 and A. Gohier 8 1 Dept. of Electronic Engineering, University of Rome Tor Vergata, Rome, Italy E-mail: *aldo.dicarlo@uniroma2.it 2 Thales Electron Devices, Vélizy, France 3 Physikalisches Institute, Goethe-Universität Frankfurt am Main, Frankfurt am Main, Germany 4 Thales Research & Technology, Palaiseau, France 5 Selex-SI, Rome, Italy 6 Technical University of Denmark, Kgs. Lyngby, Denmark 7 UMR137 CNRS/Thales, Palaiseau, France 8 LPICM – École Polytechnique, (UMR 7647) CNRS, Palaiseau, France 978-1-4244-8660-1/11/$26.00 ©2011 IEEE 55