L-Histidine tetrafluoroborate: a solution-grown semiorganic crystal for nonlinear frequency conversion

The crystal structure, refractive indices, and phase-matching conditions for a new nonlinear optical material, l-histidine tetrafluoroborate (HFB), are reported. HFB grows readily, displays favorable mechanical characteristics, and has adequate birefringence to permit phase-matched parametric processes over much of its transparency range (250 nm to 1300 nm). The phase-matching loci and angular sensitivity for second-harmonic generation of 1064-nm light in single crystals of HFB were measured. The effective nonlinearity for HFB is comparable with that of β-barium borate (~2 pm/V), and its angular sensitivity [δ(Δk)/δθ] is somewhat smaller.