Abstract
In recent years, there has been extensive research and continuous development on second-order nonlinear optical (NLO) crystal materials due to their potential applications in telecommunications, THz imaging and spectroscopy, optical information processing, and optical data storage. Recent progress in second-order NLO ionic organic crystal materials is reviewed in this article. Research has shown that the second-order nonlinear optical properties of organic crystal materials are closely related to their molecular structures. The basic structures of ionic organic conjugated molecules with excellent nonlinear optical properties are summarized. The effects of molecular structure, for example, conjugated π electron systems, electronic properties of donor-acceptor groups, and different counter-anion effects on second order NLO properties and crystal packing are studied.
Highlights
There has been considerable interest in organic nonlinear optical (NLO) materials with large second-order optical nonlinearities due to their attractive potential applications in optical frequency conversion, integrated photonics, high-speed information processing, and THz wave generation and detection [1,2,3]
Kurtz and Perry powder technique [27] is a simple and quick experimental method which only requires the material in powder form for evaluating the Second harmonic generation (SHG) efficiency of nonlinear optical materials
4-N,N-dimethylamino-40 -N 0 -methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) [30], fundamental wavelength of 1907 nm generated by stimulated Raman scattering in pressurized hydrogen gas was used, pumped by a Q-switched Nd:YAG laser operating at 1064 nm
Summary
There has been considerable interest in organic nonlinear optical (NLO) materials with large second-order optical nonlinearities due to their attractive potential applications in optical frequency conversion, integrated photonics, high-speed information processing, and THz wave generation and detection [1,2,3]. These materials have low dispersion of their dielectric constants (refractive index) and nonlinear optical susceptibility from direct current (low frequency) to the optical frequency range, because of their dominant electronic contribution to linear and nonlinear optical material polarizability [4,5,6,7]. It is desirable to develop new organic crystals with larger NLO properties and better crystal growth abilities compared with those of DAST [22]
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