Sources of Coherent Terahertz Radiation

New results in the field of high-frequency gyrotrons, gyro-multipliers and orotrons allow one to consider these electron devices as promising candidates for the realization of powerful and available sources in Terahertz range. Electron beams with a very high compression of up to a factor of 4,400 have been obtained and selective generation at the 1st-5th cyclotron harmonics have been demonstrated in Large Orbit Gyrotrons (LOGs) at millimeter and submillimeter wavelengths at operating voltages from 50 to 250 kV. When operating at the third cyclotron harmonic (TE3,8 and TE3,9 modes in the first oscillator; TE3,5 mode in the second oscillator) output power levels of 10-20 kW have been obtained in the frequency range of 0.37-0.41 THz. Gyro-multipliers with self-exciting low-frequency sections are proposed and studied theoretically. Low-voltage orotrons have been demonstrated in the frequency range of 0.1-0.4 THz with output powers of 1.0-0.1 W and typical electrical-mechanical frequency tunability within an octave range. Using the same voltage, orotrons can achieve higher power and frequency stability within the entire Terahertz range compared with BWOs that are the most widespread devices at these frequencies.