Takeya Kei, Kamei Takayuki, Kawase Kodo, Uchida Hirohisa
Opt Lett. 2020 Oct 1;45(19):5348-5351. doi: 10.1364/OL.400235.
A large unexamined second-order nonlinear optical (NLO) process is found in a 4-N,N-dimethylamino-4'-N'-methyl stilbazolium tosylate (DAST) crystal, which has a large figure of merit among NLO crystals. In second-order NLO processes using a DAST crystal, the 111(2) process of light excitation is commonly used, involving a-axis polarized light excitation with light generation of a-axis polarized light. However, there have been few studies of other second-order NLO susceptibility processes to date. In this Letter, terahertz (THz) wave generation via second-order NLO processes based on the 133(2) second-order NLO susceptibility of the DAST crystal was investigated. By adjusting the polarization direction of the excitation light using a prism-coupled Cerenkov phase-matching method, efficient generation of THz waves was achieved using a process involving 133(2). The magnitude of the NLO constant 133(2) estimated from the THz intensity ratio was 77.8 pm/V. These results indicate that prism-coupled Cherenkov phase matching can be used to identify undiscovered NLO processes for NLO crystals.
在对甲苯磺酸4-N，N-二甲基氨基-4'-N'-甲基二苯乙烯鎓（DAST）晶体中发现了一种未被深入研究的二阶非线性光学（NLO）过程，该晶体在NLO晶体中具有较大的品质因数。在使用DAST晶体的二阶NLO过程中，通常采用光激发的111(2)过程，即涉及a轴偏振光激发并产生a轴偏振光。然而，迄今为止，对其他二阶NLO极化率过程的研究很少。在本信函中，研究了基于DAST晶体133(2)二阶NLO极化率通过二阶NLO过程产生太赫兹（THz）波的情况。通过使用棱镜耦合切伦科夫相位匹配方法调整激发光的偏振方向，利用涉及133(2)的过程实现了太赫兹波的高效产生。根据太赫兹强度比估算的NLO常数133(2)的大小为77.8 pm/V。这些结果表明，棱镜耦合切伦科夫相位匹配可用于识别NLO晶体中未被发现的NLO过程。
