Investigation of third-order optical nonlinearity in KBe2BO3F2 crystal by Z-scan

Abstract

The third-order optical nonlinearity of deep-ultraviolet (DUV) nonlinear optical (NLO) crystal KBe2BO3F2 (KBBF) was investigated using single-beam Z-scan technique for the first time. The Z-scans were performed on a c-cut KBBF crystal and a KBBF prism-coupling device (PCD) with picosecond pulses at 355 nm. No two-photon absorption was observed in the experiment. The measured nonlinear refraction index n2 showed positive signs, indicating self-focusing Kerr effects. The n2 values were estimated to be (1.75±0.35)×10−15 cm2/W with the c-cut sample and (1.85±0.37)×10−15 cm2/W with the PCD, corresponding to the third-order nonlinear optical susceptibilities \(\chi_{\mathrm{eff}}^{(3)}\) of (0.99±0.20)×10−13 esu and (0.94±0.19)×10−13 esu, respectively. The results are expected to promote the investigation of frequency conversion processes with ultra-short laser in KBBF crystal.