Amplification of the Zeroth Order Mode in Ultra-thin Layers

摘要： The ultra-thin limit regime is characterized by a structure which at least in one dimension is signi?cantly smaller than the incoming light wavelength. The absorption in this regime is characterized either by very weak absorption or by a broad peak attributed to the zeroth order Fabry-Perot mode. We show that this mode provides a 14.5% ultimate ef?ciency in a 25 nm GaAs slab on a gold substrate. GaAs in air achieves only a 5% for a 10 nm slab. Such an ampli?cation of the resonance absorption is attributed to the high losses of the substrate. For very high losses, the zeroth order mode transits from an over-damped regime to an under-damped one.