Focusing effects in nonlinear resonant four-wave mixing (RFWM) MIR and FIR generation

Summary The influence of pump beam geometry in a NH₃ superradiant Raman FIR laser with RFWM generation of MIR emission has been analysed. We have observed that, in general, MIR radiation is emitted in a stimulated configuration, so pump and MIR beam overlap is basically important to exhibit an efficient RFWM. In particular, strong focusing, also in the presence of self-focusing, shows a lowering of the threshold of Raman FIR emission, as expected, plus a reduction of RFWM MIR emission. COMB-Arrich., CRE Frascati.