采用提拉法生长出了Yb:YxLu1-xVO4混合晶体,XRD测试发现该晶体具有四方Zr Si O4结构,经计算晶胞常数为a=b=0.7126(2)nm,c=0.6259(7)nm。利用化学腐蚀法和同步辐射X射线形貌术,分析了晶体中的缺陷,发现位错和小角度晶界是晶体中的两种主要缺陷。利用Read-Shockley公式计算分析了晶体中的转向小角度晶界,发现Yb:YxLu1-xVO4晶体中存在伯格斯矢量为[100]的位错。分析了晶体中位错和小角度晶界的形成原因,认为晶体生长和退火过程中的温度波动容易在Yb:YxLu1-xVO4晶体内部引起局部晶格畸变,诱发位错和小角度晶界的产生,因此混合晶体生长过程需要更精确控制。
We design an actively tunable polarization-sensitive multiband absorber in the mid-infrared region,which consists of stacked graphene multilayers separated by dielectric layers on a metal mirror.Benefiting from the anisotropic structure,the absorber has dual absorption bands with almost perfect absorption at different wavelengths under the x and y polarizations.Analyzing the electric field amplitude distributions and the surface currents,we find that the absorption peaks under the same polarization are excited in the graphene layers independently.Therefore,more absorption bands can be achieved by increasing the graphene layers.Adjusting the Fermi energy of the graphene layers,the working wavelengths of the polarization-sensitive multiband absorbers can be tuned actively,and thus achieving a wide band regulation range.Besides,the peak number and the peak strength of the multiband absorber can be actively controlled by the polarization angle as well.We also propose a method to design an actively tunable polarization-sensitive multiband absorber,which may have potential applications in mid-infrared devices,such as polarization-sensitive filters and detectors.
