Abstract
We demonstrated backward terahertz-wave parametric oscillation and used optical injection for the forward-
propagating idler to increase the output power, reduce the threshold, and stabilize the oscillation.
We generated backward-propagating terahertz-wave pulses with a high peak intensity of about 200 W at
0.3 THz. Terahertz-wave imaging was performed using our developed backward terahertz-wave parametric
oscillator to confirm its suitability for nondestructive testing applications. Due to the long-time
stability of terahertz-wave oscillation, transmission images with good visibility and inside information
were obtained by point scanning imaging. As a result of measuring various materials, we found that the
system is applicable to versatile nondestructive inspection applications.
