Second-harmonic generation in sodium lanthanium fluoride

Sodium lanthanum fluoride (NaLaF4) is a new nonlinear fluoride crystal that can be phase matched at 1.06 μm. It has an unusually small angular sensitivity for a critically phase-matchable material (800 cm−1/rad). Its nonlinear coefficients are at least 5 times larger than those of BaZnF4 and twice as large as those of Na2SbF6, the only other fluorides known to be phase matchable at 1.06 μm. This paper describes measurements of phase-matched second-harmonic generation in small (submillimeter) crystals and discusses the relationship of the observed nonlinear properties of the unusual structure of this crystal.