Nonlinear Optical Behavior Due to Charge Transfer within Selected Heterocyclic Anthracenyl Chalcones under Continuous Wave Laser Excitation

Three new heterocyclic-chalcone (HC) derivatives consisting of the π-conjugated system attached to anthracene moiety were proposed for nonlinear optical properties and optical limiting application. The NLO behavior is confirmed through obtained χ³ by Z-scan method. The closed aperture z-scan showed the HC possesses a self-defocusing effect with a negative nonlinear refractive index, <i>n</i>₂ ∼ 10⁻⁸cm/W, with a magnitude of real part of the third-order nonlinear optical susceptibilities, Re χ⁽³⁾ of the order of 10⁻⁷esu. Open Z-scan results showed that the HC samples demonstrate a reverse saturable absorption (RSA), β ∼ 10⁻⁴cm/W, corresponding to large imaginary parts, Im χ⁽³⁾ in the order of 10⁻⁶esu. Overall, the Z-scan analysis unveils an excellent value of χ³ in order of 10⁻⁶ which indicates good nonlinear material under 532 nm continuous wave laser. The optical limiting study reveals that AC exhibit a strong limiting behavior with action beginning from 0.8 KW/cm², and seems to be promising optical limiting candidates for future optoelectronic applications. Through B3LYP/6-311G++d,p level of theory Density Functional Theory (DFT), Global Reactivity, Natural Bond Orbital (NBO), and Natural Population were calculated and investigated. Delocalization and hyperconjugation interactions, intramolecular charge transfers, and stabilization energies were discovered using NBO and NPA. The comprehensive studies of Hirshfeld surface (HS) and fingerprint plots (FP) calculations were done in order to evaluate the nature of intermolecular interactions in the compounds. The inclusion of a strong donor and the π-conjugated system improved charge transfer, chemical stability, and optoelectronic properties of the anthracene-heterocyclic chalcone derivatives. As a result, the present work realizes the potential of designed derivatives that can be used in NLO applications.

本研究提出三种以π共轭体系连接蒽基团的新型杂环查尔酮（heterocyclic-chalcone, HC）衍生物，用于非线性光学（nonlinear optical, NLO）性质研究与光限幅应用。通过Z扫描法（Z-scan method）测得的三阶非线性极化率χ³，验证了其NLO行为：闭孔Z扫描实验结果显示，该HC衍生物具备自散焦效应，其非线性折射率n₂约为10^−8 cm/W，三阶非线性光学极化率的实部Re χ^(3)量级达10^−7 esu；开孔Z扫描实验结果表明，该HC样品表现出反饱和吸收（reverse saturable absorption, RSA）特性，其吸收系数β约为10^−4 cm/W，对应三阶非线性光学极化率的虚部Im χ^(3)量级为10^−6 esu。综上，Z扫描分析揭示其χ³值可达10^−6量级，表明在532 nm连续波（continuous wave, CW）激光辐照下，该材料为性能优异的非线性光学材料。光限幅研究结果显示，AC材料展现出优异的光限幅性能，其光限幅起始阈值为0.8 KW/cm²，有望成为未来光电子（optoelectronic）应用领域极具潜力的光限幅候选材料。本研究采用B3LYP/6-311G++d,p理论级别，对密度泛函理论（Density Functional Theory, DFT）相关的全局反应性参数、自然键轨道（Natural Bond Orbital, NBO）与自然布居（Natural Population）开展了计算与表征；借助NBO与自然布居分析，揭示了离域作用、超共轭相互作用、分子内电荷转移及稳定化能等关键特性。此外，本研究通过希尔施费尔德表面（Hirshfeld surface, HS）与指纹图谱（fingerprint plots, FP）的系统性计算，剖析了该类化合物分子间相互作用的本质。引入强给体基团与π共轭体系后，该类蒽基杂环查尔酮衍生物的电荷转移能力、化学稳定性及光电子性能均得到显著提升。综上，本研究证实了所设计的衍生物在非线性光学应用中具备可观的应用潜力。