Admittance matching analysis of perfect absorption in unpatterned thin films

Unified theory for perfect absorption in ultrathin absorptive films with constant tangential electric or magnetic fields

“…On the other hand, if the tangential magnetic field is almost constant inside the absorber film, we get Re( ) Im( ) 0 , Feng et al [39] and Badsha et al [43], and experimentally verified by Zhong et al [41] by using metamaterials and Luk et al [42] by using indium tin oxide just above the plasma frequency. In practice, several methods to obtain near-zero permittivity or permeability have been proposed, which can be found in Ref.…”

“…In practice, several methods to obtain near-zero permittivity or permeability have been proposed, which can be found in Ref. [42][43][44][45][46][47][48].…”

“…With the thickness much smaller than the wavelength, the phase change of waves inside the film is often negligible, and usually either the tangential electric or magnetic field is almost constant across the ultra-thin film. Various types of ultra-thin absorbers have been studied in various frequency regimes, including conductive films in microwave and terahertz (THz) regimes [1,[23][24][25], metal in optical regimes [23], organic materials [26], semi-conductors [27][28][29][30][31][32], graphene [33,34], magnetic materials [35,36], epsilon(mu)-near-zero media [37][38][39][40][41][42][43], metamaterial absorber with strong magnetic responses [44], etc. It is known that for such ultra-thin films, the absorption rate is up to 50% in symmetrical environment [1,33,45,46].…”

Theory of epsilon-near-zero modes in ultrathin films

“…We have further shown that the behaviors given by this very simple case are rather robust, since we can find the same behaviors in very different geometries and for different materials. This paves the way to very interesting possibilities, particularly in semiconductors, in which such ultrathin layers can be easily fabricated, and opens up possibilities in many applications, such as directional perfect absorption [19,28,29] [27], electro-optical modulation [30], and ultrafast thermal emission [16,31].…”

What is an epsilon-near-zero mode?

“…2 allow us to understand which material systems can support an ENZ mode and under which conditions. This paves the way to very interesting possibilities, particularly in semiconductors, where very thin layers can be easily fabricated, and opens up possibilities in many applications, such as directional perfect absorption [7][8][9], ultrafast voltage-tunable strong coupling with metamaterials [10], electro-optical modulation [11], and ultrafast thermal emission [4,12].…”