Experimental and theoretical investigations of the first and second order optical susceptibilities of BiB3O6 single crystal

The first and second order optical susceptibilities of BiB₃O₆ are calculated using the full potential linear augmented plane wave method. We find that BiB₃O₆ is a semiconductor with an indirect energy gap of 3.97 eV, to be compared to the experimental value of 4.55 eV. The calculations of the first order optical susceptibilities are compared with our measurements. We present results for the birefringence, and real and imaginary parts of the frequency dependent linear and nonlinear optical response. The calculated birefringence at zero energy is negative, in agreement with our experiments. We calculated and measured the refractive indices, and good agreement is found. Calculations are reported for the frequency dependent complex second order nonlinear optical susceptibilities χ_abc ⁽²⁾(ω). BiB₃O₆ exhibits a larger second harmonic generation efficiency than other known materials, such as lithium borate, KTiOPO₄, and BaB₂O₄. Our X-ray photoelectron spectroscopic (XPS) technique measured the concomitant photoemitted electrons with discrete kinetic energies that characterize the emitting atoms and their bonding states. Our XPS measurements show that the BiB₃O₆ structure contains parallel layers of six-fold coordinated Bi atoms alternating with borate layers, which are constituted by BO₄ tetrahedra and BO₃ triangles. PACS 71.15.Ap; 78.40.Fy; 78.20.Ci; 61.50.Ks; 71.15.Mb