Ultra-narrow band perfect absorbance induced by magnetic lattice resonances in dielectric dimer metamaterials

Nanostructured dielectric metamaterials have received extensive attention in the field of nanophotonics owing to their low radiative losses and coexisting electric and magnetic lattice resonance features. Unfortunately, suffering from the poor electromagnetic field localization and weak magnetic response in the typical dielectric metamaterials, it remains challenging to simultaneously realize ultra-narrow band perfect absorbance and intensified electromagnetic field resonances. Herein, we theoretically demonstrate a kind of dielectric metamaterials formed by dielectric cylindrical dimer array that supports magnetic lattice resonances. Benefiting from the collective diffraction coupling among the powerful magnetic dipole resonance in the dielectric dimer array, the proposed dielectric metamaterials synchronously manifest ultra-narrow spectral characteristics with bandwidth less than 8 nm, perfect absorbance amplitude as high as 99.7% and strong electric/magnetic field enhancement factor. The effects of the structure parameters on the optical properties of the proposed nanostructure are investigated based on numerical simulations. The linewidth of absorbance spectrum can be narrowed down to approximately 3 nm with optimal design. These excellent optical features supported by the dielectric dimer metamaterials can be explored as a high-efficiency refractive index sensor with sensitivity of 824 nm/RIU and figure of merit as high as 242 RIU−1. This work paves an exciting way for narrow band perfect absorbance and localized field enhancement, exhibiting tremendous enormous potential in biochemical sensing, surface enhanced spectroscopy, and nonlinear nanophotonics

Seasonal dynamics and microgeographical spatial heterogeneity of malaria along the China–Myanmar border

Malaria transmission is heterogeneous in the Greater Mekong Subregion with most of the cases occurring along international borders. Knowledge of transmission hotspots is essential for targeted malaria control and elimination in this region. This study aimed to determine the dynamics of malaria transmission and possible existence of transmission hotspots on a microgeographical scale along the China-Myanmar border. Microscopically confirmed clinical malaria cases were recorded in five border villages through a recently established surveillance system between January 2011 and December 2014. A total of 424 clinical cases with confirmed spatial and temporal information were analyzed, of which 330 (77.8%) were Plasmodium vivax and 88 (20.8%) were Plasmodium falciparum, respectively. The P. vivax and P. falciparum case ratio increased dramatically from 2.2 in 2011 to 4.7 in 2014, demonstrating that P. vivax malaria has become the predominant parasite species. Clinical infections showed a strong bimodal seasonality. There were significant differences in monthly average incidence rates among the study villages with rates in a village in China being 3-8 folds lower than those in nearby villages in Myanmar. Spatial analysis revealed the presence of clinical malaria hotspots in four villages. This information on malaria seasonal dynamics and transmission hotspots should be harnessed for planning targeted control