Zeroth Order Fabry–Perot Resonance Enabled Strong Light Absorption in Ultrathin Silicon Films on Different Metals and Its Application for Color Filters

In this work, Fabry-Perot nanocavity resonance enabled strong light absorption in ultrathin single layer silicon films on different metal surfaces was investigated. It was found that the peak absorption wavelength depends on the metal underneath the silicon film in addition to the silicon film thickness. Perfect light absorption was observed in deep subwavelength ultrathin silicon films on titanium (Ti) and chromium (Cr) metal surfaces in visible spectrum, which is caused by the zeroth order Fabry-Perot resonance mode where the round-trip phase delay in the nanocavity is zero. A perfect light absorber with an ultrathin silicon film as thin as 1/27 of the absorption wavelength on titanium metal surface has been demonstrated.