| Non-linear optics and laser technology are closely integrated and are widely used in daily life and industrial production.Realizing the continuous adjustment of the laser light source from the infrared region to the ultraviolet region has always been the goal pursued in the field of laser technology.Relying on the frequency conversion function of the nonlinear optical crystal to expand the tunable range of the laser light source is a very convenient method.Therefore,the development of nonlinear optical crystals has far-reaching significance in the fields of solid-state laser technology,optical communication,national defense,medical treatment,and industry.For nonlinear optical crystals with excellent performance,it should have a large second harmonic generation（SHG）effect,a wide optical band gap,and appropriate birefringence to meet phase matching.Organicπ-conjugated system crystals can better balance the relationship between SHG,optical band gap,and birefringence,and show excellent photoelectric properties.The main work of this thesis is to grow known organicπ-conjugated nonlinear optical crystals with excellent properties and explore new organicπ-conjugated system nonlinear optical crystals.Our research idea is based on（BO3）3-and（B3O6）3-inorganic planarπ-conjugated groups,and screen out the organic planarπ-conjugated groups—（C3N3O3）3-and（C4N2O3）2-similar to its structure.After exploring and filtering simple compounds,high-quality large-size KLi（HC3N3O3）·2H2O single crystals were grown,and two crystals of Ca（H3C4N2O3）2·H2O and Sr（H5C8N4O5）2·4H2O were synthesized.The main research work is as follows:1.KLi（HC3N3O3）·2H2O crystal growthThe KLi（HC3N3O3）·2H2O crystal growth research was carried out by the aqueous solution method.By adjusting the solution concentration,reducing the growth temperature,adjusting the solution flow rate,designing the seed rod and other growth process control,a series of problems such as high temperature decomposition of raw materials and explosion of impurity crystal during the growth process were solved,a higher-quality single crystal was grown,the crystal size reached 33×25×10mm3;and a series of optical and thermal property tests were carried out,showing that the crystal can achieve 266 nm quadruple frequency laser output,indicating that the crystal has very good application value.2.Exploration of Barbiturate SystemFor the study of barbiturate nonlinear optical crystals,Ca（H3C4N2O3）2·H2O and Sr（H5C8N4O5）2·4H2O were synthesized.Ca（H3C4N2O3）2·H2O crystallized in the noncentrosymmetry space group Aba2,the powder SHG effect was 1.15×KDP,the optical band gap was 3.61e V,and the birefringence was 0.49.Calculations show that the anionic group（C4N2O3）2-plays a major role in the nonlinear optical properties of the material.Sr（H5C8N4O5）2·4H2O crystallized in centrosymmetry space group P21/c,the optical band gap was 3.14e V,and the birefringence was 0.475.The work of this thesis can not only enrich the research field of ultraviolet nonlinear optical crystals,but also make the nonlinear optical crystals with excellent performance realize practical production applications. |
