THz-wave parametric oscillator with a surface-emitted configuration

We propose a surface-emitted cavity configuration for a terahertz-wave parametric oscillator that allows THz wave emission perpendicular to the crystal surface without any output coupler. The oscillating idler and pump waves are reflected at the surface of a nonlinear crystal in a single resonance cavity, satisfying the noncollinear phasematching condition. The radiated THz wave has a Gaussian profile. The measured beam quality factors (M(2)) were 1.15 and 1.25 in the horizontal and vertical directions, respectively. The measured tunable range was 0.8-2.74 THz. A test of transmission imaging using a test pattern was demonstrated.