Abstract
A wideband terahertz (THz) output network consisting of a pyramidal horn and a diamond Brewster window has been developed for 0.7-1.0-THz traveling-wave tube (TWT) amplifier and is measured at 0.325-0.5 THz owing to the limitation of the measurement facility. A pyramidal horn is designed to convert the waveguide mode into a high-purity quasi-plane polarized mode to meet the demand of the Brewster window. A diamond Brewster window plate with low THz transmission loss is fabricated via chemical vapor deposition (CVD). The plate is directly placed on the pyramidal horn with a Brewster angle. A circular window plate supporter is intended to balance the stress distribution during diamond-metal brazing. The measurement shows transmission coefficient is better than 0.85 within a wide bandwidth of 0.325-0.5 THz. This letter provides a practical way for a single diamond window structure for THz TWT amplifiers.