Over 200 W Peak-Power Cascaded Backward Terahertz-Wave Parametric Oscillator at 0.3 THz

We studied cascaded backward terahertz-wave parametric oscillation (BW-TPO) to enhance the output THz-wave power. The pump beam converted to the photon pair of counter-propagating THz-wave and co-propagating idler beam. The idler beams also acted as a pump beam for the cascaded THz-wave generation. The oscillation threshold of cascaded process was reduced 77% compared with the primary one thanks to the spectrum overlaps of counter-propagating THz waves. Furthermore, optical injection seeding to the first idler beam provided threshold reduction of the primary one. Output peak power of THz-wave reached 205 W with the pulse width of 0.78 ns at the frequency of 0.3 THz.