Large Hyperpolarizabilities of the Second Harmonic Generation Induced by Nonuniform Optical Near Fields
Large Hyperpolarizabilities of the Second Harmonic Generation Induced by Nonuniform Optical Near Fields
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DOI：
10.1021/acs.jpcc.6b08507
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发表时间：
2016-10
影响因子：
3.7
通讯作者：
M. Yamaguchi;K. Nobusada
中科院分区：
文献类型：
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作者：
M. Yamaguchi;K. Nobusada
在第一性原理计算的基础上，研究了非均匀光近场（ONF）诱导的二次谐波（SHG）的光选择规律和超极化率。根据密度泛函理论研究了对称分子对二硝基苯（pDNB）和非对称分子对硝基苯胺（pNA）的激发。通过计算对称pDNB的ONF激发动力学，证明了由于空间场的不均匀性，ONF即使在对称材料中也会引起SHG。为了定量评价ONF诱导SHG的强度，我们估计了非对称pNA在通常远场光和ONF激发下的第一超极化率β(2ω)。结果表明，当ONF源与pNA之间的距离约为10 A时，ONF激发的β(2ω)比远场激发的β(2ω)大1-2个数量级。
We studied the optical selection rules and hyperpolarizabilities of a second harmonic generation (SHG) induced by a nonuniform optical near field (ONF) on the basis of first-principles calculations. The excitations of the symmetric and asymmetric molecules para-dinitrobenzene (pDNB) and para-nitroaniline (pNA), respectively, were investigated according to the time-dependent density functional theory. By calculating the ONF excitation dynamics of symmetric pDNB, we demonstrated that the ONF causes the SHG even in symmetric materials because of nonuniformity of the field in space. To quantitatively evaluate the intensity of the SHG induced by the ONF, we estimated the first hyperpolarizability, β(2ω), of asymmetric pNA for both of the usual far-field light and ONF excitations. Our results showed that β(2ω) for the ONF excitation is 1–2 orders of magnitude larger than that for the far-field excitation when the distance between the source of the ONF and pNA is around 10 A.