Determination of third order nonlinear optical properties of L-histidinium p-toluenesulfonate (LHPT) organic single crystal
摘要
Third order nonlinear optical behavior i.e. nonlinear refraction (n2), absorption coefficient (β) and third order susceptibility χ(3) of an organic single crystal L-histidinium p-toluenesulfonate (LHPT) was investigated under the excitation of Q-switched Nd-YAG laser pulsed radiations (532 nm and 1064 nm) by Z-scan method at different intensities. The calculated values of β2, n2 and χ(3) at 532 nm were from 0.16 (cm/GW) to 0.23 (cm/GW), 1.24 × 10–4 (cm2/GW) to 2.51 × 10–4 (cm2/GW) and from 4.83 × 10–12 (esu) to 6.91 × 10–12 (esu) at beam intensities of 0.16 to 0.74 GW/cm2 respectively. The values of β3, n2 and χ(3) at 1064 nm were from 0.13 (cm/GW) to 0.65 (cm/GW), 3.20 × 10–4 (cm2/GW) to 5.37 × 10–4 (cm/GW) and 7.87 × 10–12 to 11.10 × 10–12 (esu) respectively at the beam intensities of 0.38 to 0.87 GW/cm2. Reverse saturation absorption (RSA) and positive nonlinear behavior were observed in this LHPT crystal. It was found that two photon absorption (2PA) was dominant process when excited with 532 nm radiations while three photon absorption (3PA) was the dominant process in RSA when excited with 1064 nm radiation. It was also found that the values of nonlinear absorption coefficient (β) and nonlinear refraction (n2) increase with increase of excitation intensity irrespective of excitation wavelengths. As the crystal possesses positive nonlinearity thus this crystal could be a potential candidate for practical device applications like two-wave mixing, optical limiter and switching device.