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Numerical dispersion diagrams of the silver surface grating structures with a width and depth of 100 nm and 20 nm, respectively. The grating periods are 400 nm, 450 nm (upper panel of insets), 500 nm (central panel of insets), and 550 nm (lower panel of insets). The figures show the dispersion curves, light lines in free space (dotted), and the variation in the band edge with period (indicated by arrows).
Reflection resonant spectra for different periods at the wavelength of 546 nm. The period change is 2 nm in inset (a) and 10 nm in (b). The curves have been plotted with subsequent vertical offsets of 1.
Trapped rainbow in a chirped nanograting. (a) Illustration of the chirped nanograting with adiabatically varying periods. Inset: scanning electron microscope (SEM) images of the chirped grating from the short period side (upper, ) to the long period side (lower, ). Scale bar: . [(b)–(e)] Microscope images of the trapped rainbow in the planar chirped nanograting under white light illumination (b) or at wavelengths centered at 592 nm (c), 546 nm (d), and 488 nm (e). Scale bar: .
(a) SEM image of the deep grooves fabricated on the left-hand side of the chirped nanograting. The deep grooves are placed between the input SPP coupler and the chirped nanograting to function as a surface wave filter in (b). (b) and (c) show microscope images of the trapped rainbow in the planar chirped nanograting under white light illumination.
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