Third order nonlinear optical properties and optical limiting behaviour of sodium penta borate

Studies on third order optical nonlinearity of solution grown inorganic single crystal of sodium penta borate (NaB5) was carried out by z-scan technique with Nd:YAG laser (532 nm, 50 mW). The closed aperture z-scan measurement results peak valley pattern in normalized transmittance indicates the negative nonlinear refractive index due to self-defocusing nature and the nonlinear absorption is regarded as saturable absorption due to maximum transmittance lies near the focus in open aperture curve. The third order nonlinear optical parameters refractive index, nonlinear absorption coefficient and nonlinear susceptibility were found to be -1.28 x 10(- 10) cm(2)/W, -7.91 x 10(- 6) cm/W and 2.07 x 10(- 7) esu. The optical constants (refractive index (n), reflectance (R), extinction coefficient (K), optical and electrical conductivity) of NaB5 crystals were determined by theoretical calculations from UV-Visible studies. The optical limiting property also studied for grown crystal and the limiting threshold values was found to be 35 mW.