Ge-Sb-Se硫系玻璃的折射率和热光系数

Refractive index and thermo-optic coefficient of Ge-Sb-Se chalcogenide glass

Ge-Sb-Se硫系玻璃被认为是极佳的红外传输材料和有潜力的非线性光学材料.在光学设计中,玻璃的线性折射率(n)及其热光系数(ζ)是关键技术参数.以预测和调控Ge-Sb-Se玻璃的n和ζ为目的,考察了玻璃的n,ζ,密度(d)和体积膨胀系数(β)与化学参数dSe和拓扑网络结构参数<r>的内在联系.研究发现,玻璃的n随d的增加而增大;ζ随β的增大而近似线性减小;β随dSe的减小或<r>的增大而减小;当Ge含量固定时, d随dSe的减小或<r>的增大而增大,当Sb含量固定时, d在dSe=0时具有最小值.基于实测d和n,拟合获得了Ge, Sb和Se元素在2—12μm波段的摩尔折射度(R_i),分别为R_(Ge)=10.16—10.50 cm^3/mol,RSb=16.71—17.08 cm^3/mol和RSe=11.15—11.21 cm^3/mol,根据d和R_i计算得到的n与实测值的偏差小于1%.基于实测ζ和β,拟合得到了Ge, Sb和Se元素在2—12μm波段的摩尔折射度温度系数(φ_i),分别为φ_(Ge)=21.1—22.6 ppm/K,φ_(Sb)=7.2—8.4 ppm/K和φ_(Se)=90.2—94.2 ppm/K,根据β和φ_i计算得到的ζ与实测值的偏差小于6 ppm/K.

Ge-Sb-Se chalcogenide glass is environmentally friendly, and has wide infrared transmitting window, high optical nonlinearity, as well as good mechanical property. These make it a good material for infrared transmission and nonlinear optics. In optical designs, the refractive index(n) and thermo-optic coefficient(ζ) of the glass are key technical parameters. In order to predict and tailor the n and ζ of Ge-Sb-Se glass, compositions with different chemical and topological features are prepared, their n, ζ, density(d) and volume expansion coefficient(β) are measured, and the composition dependence of the parameters is systematically investigated. The chemical feature of the glass is quantified by the percentage deviation of the composition from the stoichiometric ratio and denoted as dSe. The topological feature is represented by the mean coordination number <r> of each atom in the composition. It is shown that the n of Ge-Sb-Se glass increases with d increasing;the ζ decreases almost linearly with β increasing;and the β decreases with dSe decreasing or <r> increasing. When the Ge content is fixed, the d increases with dSe decreasing or <r> increasing;when the Sb concentration is fixed, the d has a minimum value at dSe = 0. Based on the measured d and n, the molar refractivity(Ri) of Ge, Sb and Se elements in a spectral range of 2–12 μm are calculated. The obtained value of RGeis in a range of 10.16–10.50 cm3/mol, RSbin a range of 16.71–17.08 cm3/mol, and RSein a range of 11.15–11.21 cm3/mol.When the Riand d are used to compute n of any composition, the discrepancy between the calculated value and the measured one is less than 1%. According to the measured ζ and β, the thermal coefficients of the molar refractivity(φi)of Ge, Sb, and Se elements in a wavelength region of 2–12 μm are computed. The optimal value of φGe is in a range of 21.1–22.6 ppm/K, φSb in a range of 7.2–8.4 ppm/K, and φSe in a range of 90.2–94.2 ppm/K. When the φi and β are used to compute ζ of any composition, the discrepancy between the calculated value and the measured value is less than 6 ppm/K.