Generation of mid-infrared pulses by c(3) difference frequency generation in CaF2 and BaF2

Tunable mid-IR pulses in the range 1300-4200 cm ^-1 (7.7-2.4 µm) are generated through a phase-matched four-wave mixing process in ordinary mid-IR window materials such as CaF₂ and BaF₂. In this process the difference frequency v₃ =2v₂ – v₁ is generated from pump fields v₁ and v₂. The process can be phase matched to different frequencies by adjustment of the angle between the pump fields.