Continuous wave terahertz molecular laser optically pumped by a quantum cascade laser

We demonstrate a low-threshold, compact, continuous-wave molecular laser optically pumped by a mid-infrared quantum cascade laser. NH3 molecules are pumped around 10.3 μm and de-excite by stimulated emission on pure inversion transitions. We demonstrate CW generation of ten lasers lines around 1 THz. At 1.07 THz a power of 34 μW is obtained with a low threshold of 2 mW and a high differential efficiency of 0.6 mW/W. To our knowledge this is the first THz molecular laser pumped by a solid-state source and this result opens the way for compact, simple and efficient THz source.