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Z-Scan Technique – Measurement of Third Order Non-linear Optical Properties of Ammonium Penta Borate Single Crystals
R. Ranjani, T. Sivanesan, V. Natarajan, K. Amudha and P. R. Umarani

Single crystals of Ammonium Penta Borate of dimensions 1.1 × 0.7 × 1.3 cm3 were grown using de-ionized water as a solvent by slow evaporation solution growth method and subjected to optical characterization. Good optical quality of crystal was observed and the grown crystals were characterized by single crystal X-ray diffraction study which confirms that the grown crystal belongs to P21 / c space group. The UV-Vis-NIR spectra of Ammonium Penta Borate clearly indicate the absence of absorption in the visible region. Absence of SHG (χ(2) = 0), affirms that this crystal is of Centro-symmetric class and hence the Z-scan technique is employed for THG. Through the Z-scan technique, the nonlinear refractive index n2 and the absolute value of the third order non-linear optical susceptibility χ(3) have been measured at the wavelength of 632.8nm and were found to be 1.7234 × 10-7 cm2/ W and 6.7623 × 10-7 esu respectively. Also, at the same wavelength, the real χR(3) and imaginary χI(3) parts of χ(3) have been calculated as 6.7538 × 10-7 esu and 3.4025 × 10-8 esu respectively. Ammonium Penta Borate exhibits saturation absorption and self-defocusing performance and its non-linear absorption co-efficient β is determined as 9.2286 × 10-4 cm / W.

Keywords: Ammonium Penta Borate, Solution growth, single XRD, UV-Vis-NIR, Z-Scan, THG.

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