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Generation of ∼100  kW narrow-line far-infrared radiation from a KTP off-axis THz parametric oscillator

In the far-infrared spectrum between 20 and 60 μm, the free-electron laser (FEL) is the only wavelength-tunable coherent radiation source capable of generating kilowatt to megawatt peak powers with a linewidth of the order of 1%. Here, we report the detection of >70  kW radiation power at about 52 μm in a 45  kW radiation power for the far-infrared radiation. With 63% coupling efficiency of the silicon prism atop the KTP crystal, the measured >70 and >45  kW far-infrared radiation correspond to >111 and >71  kW powers extracted from the KTP crystal of the seeded off-axis THz parametric oscillator. The radiation source accomplished in this work has great potential to become a tabletop and economical alternative for the bulky and expensive far-infrared FELs in national facilities.