Design,synthesis And Characteristics Of A Novel Ionic Nonlinear Optical Organic Material OHB-T

With the development of optoelectronic technology,nonlinear optical materials,especially organic nonlinear optical crystals,have become indispensable materials.The potential applications of organic nonlinear optical crystals in frequency conversion,terahertz imaging and spectroscopy,optical information processing and optical signal control have brought great opportunities for development.Due to the nonlinear optical properties are closely related to the molecular structure,various novel organic nonlinear optical crystals have been designed and developed.Most of these crystals were developed from the ionic nonlinear optical organic crystal 4-N,N-dimethylamino-4?-N?-methyl-stilbazolium tosylate(DAST),where various substitute groups were used to adjust the structures of anions and cations as well as the spatial arrangement orientation of the crystals.Accordingly,a novel ionic nonlinear optical organic material2-(4-hydroxystyryl)-3-methylbenzo[d]thiazol-3-ium 4-methylbenzenesulfonate(OHB-T)was presented in this thesis,and its design,synthesis,and characteristics were systematically investigated.The main research contents include:(1)A novel ionic nonlinear optical organic material 2-(4-hydroxystyryl)-3-methylbenzo[d]thiazol-3-ium 4-methylbenzenesulfonate(OHB-T)was designed.At the same time,the molecular structure and spatial arrangement of OHB-T crystal were determined,that is,hydroxy-styryl-benzothiazolyl is taken as D-?-A cation structure,4-methylbenzenesulfonate is taken as anion structure,and the organic small molecules composed of anion and anion are arranged orderly in space.In addition,the electronic structures(energy band and density of state)and optical parameters(complex permittivity,refractive index,and extinction coefficient,as well as absorption coefficient and reflectance)of OHB-T crystal were calculated(2)The OHB-T products were successfully synthesized and purified.The as-yield OHB-T products were systematically characterized by NMR and IR spectroscopies,X-ray diffraction analysis,Raman spectroscopy analysis,and elemental analysis.All characterization results verified that the as-synthesized products are indeed the self-designed OHB-T.(3)Based on the synthesized products,the OHB-T organic single crystals with the largest size of 3×2×2 mm~3 were successfully grown for the first time by the solution evaporation method.In addition,OHB-T polycrystalline thin films were prepared on glass substrates by spraying and annealing.(4)The nonlinear optical properties of OHB-T crystal were measured and characterized.The second harmonic generation effects of OHB-T organic single crystal and polycrystalline films were experimentally detected,and it is found that both of them can generate double frequency signal,indicating second-order nonlinearity for OHB-T.In addition,the terahertz(THz)spectrum of OHB-T organic single crystal was also studied by THz time domain spectroscopy.The result revealed that the OHB-T crystal has strong absorptions near 0.546 THz and within the range of 1.740-2.500 THz,which is expected to be used in the study of THz response and highly efficient terahertz wave generation.