Department of Physical Electronics, Tel Aviv University, Ramat Aviv, Tel Aviv69978, Israel.
The Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv69978, Israel.
ACS Appl Mater Interfaces. 2023 Feb 15;15(6):8590-8600. doi: 10.1021/acsami.2c18454. Epub 2023 Feb 2.
Organic crystals with unique nonlinear optical properties have been attracting attention owing to their capability to outperform their conventional nonorganic counterparts. Since nonlinear material responses are linked to a crystal's internal microscopic structure, molecular engineering of maximally unharmonic quantum potentials can boost macromolecular susceptibilities. Here, large-scale kainic acid (kainate) single crystals were synthesized, and their linear and nonlinear optical properties were studied in a broad spectral range, spanning the visible to THz spectral regions. The non-centrosymmetric zwitterionic crystallization, molecular structure, and intermolecular arrangement were found to act as additive donor-acceptor domains, enhancing the efficiency of the intrinsic second-order optical nonlinearity of this pure enantiomeric crystal. Molecular simulations and experimental analysis were performed to retrieve the crystals' properties. The crystals were predicted and found to have good transparency in a broad spectral range from the UV to the infrared (0.2-20 μm). Second-harmonic generation was measured for ultrashort pumping wavelengths between 800 and 2400 nm, showing an enhanced response around 600 nm. Broadband THz generation was demonstrated with a detection limited bandwidth of >8 THz along with emission efficiencies comparable to and prevailing those of commercial ZnTe crystals. The broadband nonlinear response and high transparency make kainate crystals extremely attractive for realizing a range of nonlinear optical devices.
具有独特非线性光学性质的有机晶体因其能够超越传统非有机对应物的性能而受到关注。由于非线性材料响应与晶体的内部微观结构有关，因此最大化非谐量子势的分子工程可以提高大分子的磁化率。在这里，大规模合成了 kainic 酸（kainate）单晶，并在很宽的光谱范围内（从可见到太赫兹光谱区域）研究了它们的线性和非线性光学性质。非中心对称两性离子结晶、分子结构和分子间排列被发现作为附加的给体-受体域，增强了这种纯对映体晶体固有二阶光学非线性的效率。进行了分子模拟和实验分析以获取晶体的性质。预测并发现这些晶体在从紫外线到红外线（0.2-20 μm）的很宽光谱范围内具有良好的透明度。在 800 到 2400nm 的超短泵浦波长下测量了二次谐波产生，在 600nm 左右显示出增强的响应。宽带太赫兹产生的检测带宽>8THz，发射效率可与商业 ZnTe 晶体相媲美并超过其发射效率。宽带非线性响应和高透明度使 kainate 晶体非常适合实现一系列非线性光学器件。
