With an assembly of double-layered H-shaped metallic resonators, we simultaneously realized both magnetic and electric resonances at the same frequency band. Negative refractive index (NRI) is consequently achieved. The frequency band with NRI can be tuned by the structural parameters of the H-shaped resonators. This design demonstrates a unique example to construct metamaterial with NRI feature.

We proposed a diffractive method of absolute measurement of groove spacing for plane varied-line-spacing (VLS) gratings based on the long trace profiler. It was demonstrated over sub-nanometer measurement accuracy in determining the groove spacing of a grating with grooves varying in sub-micrometer scale along its surface. Being sensitive to angle measurement (sub-grad), the long trace profiler (LTP) was used to measure the groove density (or the groove density variation) of a surface diffraction grating along its longitudinal direction. Based on Littrow mounting configuration, the accuracy of groove density measurement exceeded X 10-4 on the whole surface.Equipped with one linear guide, it easily afforded twodimensional measurement of groove density for a diffraction grating quickly.