Generation of sub-100-kW narrow-line far-infrared radiation from KTP off-axis THz parametric oscillator seeded by a spectrally filtered Stokes pulse

We report the detection of $> 70 -$kW radiation power at about $52 \mu$ m from a KTP off-axis THz parametric oscillator, when pumping it with 11.9-mJ energy in a 450-ps pulse from a single-frequency Nd:YAG laser and seeding it with a 7-μJ, 40-GHz-linewidth Stokes pulse from a synchronously pumped KTP parametric generator. With 63% coupling efficiency of the silicon prism, the seeded off-axis THz parametric oscillator has emitted $> 111 -$kW peak power radiation into the silicon prism.