Abstract
Nonlinear optical crystals of LiNbO3 have fascinated industry and fundamental research since their
invention. The potential of the crystals continually indicates excellent and novel properties in terahertz
(THz)-wave spectral region as well. Using bulk crystal, intense THz-waves of kilowatt-level peaks was
demonstrated with wide frequency tunability from sub-THz to 4.5 THz. Additionally, sensitive THzwave
detection on the order of atto-joule energy was obtained by up-conversion from THz-wave to nearinfrared
light. To produce more effective and practical devices, periodically poled LiNbO3 (PPLN) was
designed. A compact device for THz-wave detection was achieved. Especially, backward THz-wave
parametric oscillation was obtained in PPLN with wide wavelength tunability and narrow spectral
bandwidth with no cavity structure, which is anticipated as a promising THz-wave source because of its
simple structure and lack of mode-hopping during wavelength tuning.
