Enhancement of the output power of a terahertz parametric oscillator with recycled pump beam

We report a technique for the terahertz parametric oscillator, in which we recycle the pump beam in order to increase the efficiency and enhance the terahertz beam output. In our experiments, the pump laser beam is injected into a doped LiNbO3 crystal with 5% MgO, and the exiting pump beam is redirected back through the nonlinear crystal. Our data show that the terahertz beam output power increases almost four times in magnitude, when the pump beam is recycled once in crossed-beam geometry.