High-Power High-Brightness Terahertz Source Based on Nonlinear Optical Crystal Fiber

A nonlinear crystal fiber converter for terahertz (THz) difference frequency generation (DFG) is proposed. This axisymmetric structure consists of a periodically inverted GaAs core clad with index-matched chalcogenide glass, which functions as a single-mode fiber for THz radiation to prevent its diffraction and achieve efficient optical-to-THz conversion. The process of DFG between ps-pulses in the crystal fiber is investigated by developing the guided-wave coupled-mode equations for quasi-monochromatic pulses. The output power, spectral power density, and brightness are analyzed, based on the calculations of the dynamic of energy conversion and the characteristics of the THz beam focusing. High output power as well as excellent beam quality contributes to the high brightness of the presented THz crystal fiber source.