论文标题
铁电氧化物的非线性光学响应：时域和频域内的第一原理计算
Nonlinear optical response of ferroelectric oxides: first-principles calculations within the time-domain and the frequency-domain
论文作者
论文摘要
铁电氧化物Linbo $ _3 $，LITAO $ _3 $和KNBO $ _3 $的第二和三阶非线性敏感性是根据第一原则计算得出的。比较了两种不同的方法，一种方法是基于频域内的扰动方法，另一种方法基于电动极化的时间进化。在两种方法中计算出的linbo $ _3 $的铁电相的第二个谐波系数的频率依赖性是非常一致的。 Linbo $ _3 $和LITAO $ _3 $的实验数据进一步验证了这一点，该数据以0.78 eV和1.6 eV之间的光子能量事件范围进行测量。此外，还采用了基于实时的方法来估计所有研究的铁电氧化物的三阶非线性敏感性。我们进一步表明，通过与计算有效的独立粒子近似相结合的剪刀偏移来考虑的Quasiparticle效应，导致所有光谱特征向更高的能量降低并降低光学非线性的幅度。超极化能力中主要共振的能量表明，可以通过在所有研究材料的基本带隙内的多光子吸附来理解光谱。
The second and third order nonlinear susceptibilities of the ferroelectric oxides LiNbO$_3$, LiTaO$_3$, and KNbO$_3$ are calculated from first principles. Two distinct methodologies are compared, one approach is based on a perturbative approach within the frequency-domain, another on the time-evolution of the electric polarization. The frequency dependence of the second harmonic coefficients of the ferroelectric phase of LiNbO$_3$ calculated within the two approaches is in excellent agreement. This is further validated by experimental data for LiNbO$_3$ and LiTaO$_3$, measured for an incident range of photon energies between 0.78 eV and 1.6 eV. The real-time based approach is furthermore employed to estimate the third order nonlinear susceptibilities of all investigated ferroelectric oxides. We further show that the quasiparticle effects, considered by means of a scissors-shift in combination with the the computationally efficient independent particle approximation, result in a shift all spectral features towards higher energies and decrease the magnitude of the optical nonlinearities. The energy of the main resonances in the hyperpolarizabilities suggests that the spectra can be understood by multi-photon adsorption within the fundamental bandgap for all investigated materials.
