Generation of coherent radiation at 89.6 nm through two-photon resonant phase-matched tripling of fourth-harmonic Nd: Glass laser radiation in Hg vapors

Coherent radiation at 89.6 nm has been obtained through third-harmonic conversion of the 268.8 nm pulses in mercury vapors. Tunability of the fourth-harmonic frequency of the Nd: glass laser radiation to the 6s ¹ S ₀–8s ¹ S ₀ double quantum resonance of Hg atoms has been used for the resonant enhancement of the twelfth-harmonic output. Possibility to phase match the generated radiation and driving polarisation in pure vapors without employing of bufer gas has been demonstrated.