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Abstract
A mechanism not based on the traditional thermodynamics effect but on the microscopic origin of the nonlinear effect was investigated for full consideration of the correlation between the e-beam irradiation electric field (IEF) and the properties of the nonlinear material BBO (β-BaB2O4). Firstly, the IEF magnitude is computed under different conditions of beam intensity, ray energy and radiation dose. Secondly, the relationship model of IEF and nonlinear coefficients is built according to quantum mechanics principle. The results show that low-energy irradiation of 0–400 MeV ray energy (corresponding to IEFs of 0–12 × 10−4 a.u.) has no obvious effect on the nonlinear optical properties of BBO crystals. When the energy is higher than 420 MeV (corresponding to an IEF of 13 × 10−4 a.u.), the hyperpolarizability changed significantly, indicating permanent damage of the BBO crystals. With an increase of the ray energy, βx and βy tend to decrease, but βz increases markedly especially when the ray energy is more than 450 MeV (corresponding to an IEF of 16 × 10−4 a.u.).
Acknowledgements
This work was supported by the National Natural Science Foundation of China (No. 10805001) and by the Key Project of Chinese Ministry of Education (No. 210099).