Supplementary material

In supplementary material are provided D2O and H2O laser line lists for both bending and stretching vibrational modes. In these tables, THz laser frequencies and QCL pump frequencies, associated to their respective molecular gain factor, are reported. All these transitions show a molecular gain factor above 10^−20 uGm, which is the current threshold for our laser. Figure S1 shows D2O and H2O laser lines exhibiting molec- ular gain factors above 10^−20 uGm, obtained by pumping the symmetric and antisymmetric stretching band.