Band Compression of Plasmonic Filters

We demonstrate theoretically and experimentally the difference between the band compression mechanisms of plasmonic gratings and plasmonic heterogratings. The plasmonic grating can pick out a fixed polarization bandwidth with changing the incidence angle, while the plasmonic heterograting composed of two different nanogratings can pick out a tunable bandwidth with changing the incidence angle and the period ratio of two gratings. The range of the plasmonic resonances of the heterograting is about 30% wider than that of a conventional grating. Thus, the plasmonic heterograting can work efficiently in a wider wavelength range. Moreover, high polarization extinction ratio is achieved in these plasmonic devices. This gives more insights into the mechanisms in plasmonic filters and is helpful to promote the actual applications.