Far-infrared laser emission by microwave-infrared-far-infrared three-photon interaction in NH3

We report low threshold Raman and hyper-Raman far-infrared laser emission associated with the
¹⁴
NH
3
,
\nu_{2}, sQ(5, 4)
infrared transition. Using a circular metallic waveguide FIR resonator, which also acts as a microwave resonator, threshold pump powers were 50 W CO
2
-laser radiation and 150 W CO
2
, 15 W microwave for Raman and hyper-Raman emission, respectively. The hyper-Raman process is suitable to generate frequency-tunable FIR radiation.