Narrowed intermediate resonance in multiresonant four-wave mixing in LiTbF(4).

A new technique for overcoming inhomogeneous broadening in condensed matter is reported. Phase-matchinginduced frequency selectivity associated with multiresonant four-wave mixing is explored in detail for the first time to our knowledge and shown to give laser-limited linewidths that are more than 10 times narrower than the inhomogeneous width of an intermediate resonance in LiTbF (4). The anomalous dispersion associated with the resonance. was also measured, and model calculations suggest that significantly greater narrowing is feasible.