Growth, Band Structure and Optical Properties of LiSrBO3 Crystal

The bulk crystal of LiSrBO3 (8.39 g) with a size of 21mm×20mm×15mm was grown by high temperature solution growth method. The relationship between growth habit and crystal structure was discussed. The transmission spectrum shows an UV absorption edge at about 300 nm. The melting temperature of this crystal was determined to be 942 ℃ by DTA-TG measurement. The band structure of the LiSrBO3 crystal was studied by means of the first principle method. An indirect band gap was found to be about 4.0 eV,and a low dielectric constant was estimated to be about 1.9 in terms of theoretical results.     

Li3AlB2O6： Synthesis, Crystal Structure, and Its Luminescence Property Compared with LiSrBO3

The synthesis and crystal structure of Li3AlB2O6 with different cell parameters are reported and these cells are transformed each other from the confirmation of crystallographic structural analyses. The absorption spectrum, luminescence and lifetimes of the Li3AlB2O6 and LiSrBO3 solid compounds are measured and the comparisons are made between them. It is shown that the absorption edges are at about 400 nm (or band gap 3.1 eV) and there is one of absorption peaks at about 350 nm for the Li3AlB2O6 and LiSrBO3. The emission band (530 nm) makes a red shift and fluorescence decay time (24.39 ns) of the Li3AlB2O6 becomes smaller compared with the emission band (480 nm) and lifetime (93.16 ns) of the LiSrBO3 at the visible region. The transition energies and oscillator strengths of the clusters (Li3AlB2O6)2 and (LiSrBO3)2 lying at low excited states are calculated by the time-dependent Hartree-Fock method. The obtained results are used to model the photophysical properties and discuss the origin of spectral bands of the Li3AlB2O6 and LiSrBO3.     

掺质KTP型晶体生长与性能研究

采用高温溶液法生长了含掺质离子Zr4+,Ga3+的单掺和双掺系列KTP型晶体.晶体生长过程中发现Ga掺入溶液后,体系更加稳定,容易生长出光学质量的晶体;而Zr掺入溶液后体系稳定性降低,晶体生长较困难.用等离子体发射光谱测定了各掺质离子在晶体中的含量,计算出掺质离子的分配系数,发现生长体系中Ga无论是在高掺入量还是低掺入量的情况下,Ga在晶体中的含量都十分稳定.测定了晶体的晶胞参数、紫外-可见-红外吸收光谱,测定的结果发现,晶胞参数均变化不大,在吸收光谱中Ga:KTP在可见光谱区有少量的光吸收,而Zr:KTP晶体是无色透明的.通过粉末倍频实验发现,Zr的掺入有助于晶体倍频转换效率的提高.通过晶体c轴向离子电导率的测试发现,Ga的掺入使c轴向电导率降低了大约3个数量级.双掺Zr和Ga的晶体是性能更为优良的掺质KTP型晶体.     

非线性光学晶体HgGa2S4 和 Hg0.5Cd0.5Ga2S4的能带结构、化学键及光学性质研究

用密度泛函理论和非谐振子模型计算了晶体HgGa₂S₄和Hg_0.5Cd_0.5Ga₂S₄的能带结构、态密度、化学成键及线性、非线性光学性质。结果表明：HgGa₂S₄的价带顶部主要是Ga-S成键态的贡献，导带底部主要是Ga-S反键态的贡献; Hg_0.5Cd_0.5Ga₂S₄的价带顶部主要由S-3p轨道组成，导带底部主要是Ga-S反键态的贡献。布居分析表明Ga-S键主要是共价成分，而Hg-S和Cd-S键主要是离子成分。HgGa₂S₄的折射率计算值与实验值在低能量区很好吻合。另外，HgGa₂S₄的能隙计算值比Hg_0.5Cd_0.5Ga₂S₄小，而二阶非线性极化率比Hg_0.5Cd_0.5Ga₂S₄大。