Effect of the coherent cancellation of the two-photon resonance on the generation of vacuum ultraviolet light by two-photon resonantly enhanced four-wave mixing

Many of the most impressive demonstrations of the efficient generation of vacuum ultraviolet (VUV) light have made use of two-photon resonantly enhanced four-wave mixing to generate light at ω_VUV =2ω_L1±ω_L2. The two-photon resonance state is coupled to the ground state both by two photons from the first laser, or by a photon from the second laser and one from the generated VUV beam. We show here that these two coherent pathways destructively interfere once the second laser is made sufficiently intense, thereby leading to an important limiting effect on the achievable conversion efficiency.