Abstract
Organic second-order nonlinear optical materials are of great significance in the field of integrated photonics, optical data storage and optical information processing. In this work, two iodide salts with benzo[e]indol cations as electron-withdrawing groups were designed and synthesized, which are (E)-2-(4-hydroxy-3-methoxystyryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (1-TB) and (E)-2-(3,4-dihydroxystyryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (2-TB). Under the irradiation of 1064 nm laser, the second harmonic generations of the 1-TB and 2-TB powders are 760 and 580 times that of urea, respectively. Among them, crystals of 1-TB are successfully grown by a slow cooling method without using seed crystals. Bulk crystal with a size of 8.0 × 3.0 × 1.0 mm3 and many submillimeter single crystals with excellent optical quality are obtained.
Highlights
With the development of the information age, optoelectronic technology has gradually become the main pillar of information technology in the 21st century [1,2,3,4,5,6,7,8]
(2-(4-hydroxy-3-methoxystyryl)-3-methylbenzo[d]thiazol-3-ium) series single crystals have the same order of magnitude of nonlinear optical susceptibilities as DAST and DSTMS [20,21,22]
The 1-TB and 2-TB are designed as D-π-A delocalized systems with benzo[e]indol cation as the electron-withdrawing group and pair-arranged combination to provide electrons [25]. It is well-known that a necessary requirement for the generation of second-order nonlinearity is the noncentrosymmetric arrangement of the chromophore molecules
Summary
With the development of the information age, optoelectronic technology has gradually become the main pillar of information technology in the 21st century [1,2,3,4,5,6,7,8]. To obtain an organic single crystal that satisfies the strong macroscopic second-order nonlinear optical characteristics of laser frequency conversion and terahertz wave generation, the preparation of a large first-order hyperpolarizabilities β of chromophore is the primary premise. The 1-TB and 2-TB are designed as D-π-A delocalized systems with benzo[e]indol cation as the electron-withdrawing group and pair-arranged (hydroxy, methoxy) combination to provide electrons [25] It is well-known that a necessary requirement for the generation of second-order nonlinearity is the noncentrosymmetric arrangement of the chromophore molecules. I hydrogen bond can reduce the energy of the whole system and keep it more stable [27,28,29] These advancements indicate that the 1-TB is an organic second-order NLO salt material with promising applications
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