Harmonics generation and intense terahertz radiation from polar   molecules at multiphoton resonant excitation in laser fields
  The coherent radiation spectrum of two-level polar molecules with UV transition is studied at the multiphoton resonant excitation by a moderately strong laser field. The spectrum corresponding to harmonic generation and low-frequency radiation is investigated both analytically and numerically. Specifically, a mechanism for generation of intense smoothly tunable terahertz radiation by two-level molecular configurations (with dynamic Stark shifts) possessing permanent dipole moments, is considered. 
H.K. Avetissian, B.R. Avchyan, G.F. Mkrtchian
physics.atom-ph physics.optics quant-ph