Optical properties and crystal growth of lead tetraborate

Abstract

This paper reports growth and optical properties of PbB 4O 7, a new host for χ (2)-type nonlinear optical interactions. Large, inclusion-free single crystals (20 × 8 × 8 mm 3) of PbB 4O 7 have been grown from self-flux and stoichiometric melts contained in Pt crucibles, using a resistance heated furnace. The crystal has an orthorhombic structure, with space group P2 1 nm. The optical absorption spectrum is essentially featureless from the band edge near 300 nm through the visible and near infrared regions. The principal indices of refraction have been measured with high accuracy using a modified angle of deviation technique. These crystals are optically biaxial, point symmetry mm2: their non-zero d-coefficients d 15 = d 31, d 24 = d 32 and d 33 have been measured using the Maker fringe technique. The optical properties are compared with those of other nonlinear optical crystals and related to the differences in their respective structures.