Experimental results for the microwave band: (a) Photographs of the fabricated samples. The lattice constant of the two samples is d = 20 mm, the slit width is a = 1 mm, and the grating thickness is h = 5 mm and 10 mm, respectively. The measured (the circles) and calculated (the line) reflection spectra are presented in (b) for h = 5 mm, t = 0.15 mm and (d) for h = 10 mm, t = 0.3 mm, respectively. The measured (the circles) and calculated (the lines) resonance wavelength of the two samples as a function of spacer thickness t are shown in (c), h = 5 mm, and (e), h = 10 mm, respectively.