A tunable terahertz-wave source has been realized by Optical Parametric Oscillator (OPO) utilizing the polaritonmode scattering of LiNbO3. This technique has several advantages such as wide tunability and compactsystem. In this paper, we demonstrate an efficient terahertz-wave radiation by using a new OPOconfigurationwith a trapezoidal LiNbO3 crystal. A tunable range of 130-310 μm has been achieved without a couplingdevice. This method reduces an influence of the propagation loss in the crystal, so that the shorter wavelengthoscillation is enhanced.
