Theory of absorption-induced transparency

Abstract

Recent experiments [Hutchison, O'Carroll, Schwartz, Genet, and Ebbesen, Angew. Chem. Int. Ed. 50, 2085 (2011)] have demonstrated that optical transmission through an array of subwavelength holes in a metal film can be enhanced by the intentional presence of dyes in the system. As the transmission maximum occurs spectrally close to the absorption resonances of the dyes, this phenomenon was christened "absorption induced transparency". Here, a theoretical study on absorption induced transparency is presented. The results show that the appearance of transmission maxima requires that the absorbent fills the holes and that it occurs also for single holes. Furthermore, it is shown that the transmission process is nonresonant, being composed by a sequential passage of the electromagnetic field through the hole. Finally, the physical origin of the phenomenon is demonstrated to be nonplasmonic, which implies that absorption induced transparency should also occur at the infrared or terahertz frequency regimes.

Plasmonic electrodes for bulk-heterojunction organic photovoltaics: a review

“…156,157 This transparency, which is separate from the EOT effect, occurs at wavelengths slightly redshifted from the absorption peak of the absorbing material. This phenomenon, called absorptioninduced transparency (AIT), is still not fully understood but is proposed to be due to either coupling to an SPP 156 or a change in the imaginary part of the propagation constant of the combined hole-absorber "waveguide."…”

“…This phenomenon, called absorptioninduced transparency (AIT), is still not fully understood but is proposed to be due to either coupling to an SPP 156 or a change in the imaginary part of the propagation constant of the combined hole-absorber "waveguide." 157 The AIT phenomenon has also not yet been explored for use in BHJ-OPVs, but in cases where nanohole arrays are used as transparent electrodes, AIT could potentially play an important role in increasing the absorption enhancement factor in the active layer. In addition to exhibiting unique optical properties, metallic electrodes consisting of nanohole arrays can exhibit lower resistivity compared to ITO, making them viable transparent plasmonic front electrodes for OPV applications.…”

Terahertz gas sensor based on absorption-induced transparency

“…Experimentally observed for electronic transitions in the visible range [14], and subsequently for molecular vibrational transitions in the infrared regime [17], it was later predicted that AIT could occur also in other frequency bands, as in the THz regime [11]. This prediction has been experimentally confirmed [18] with the use of lithium fluoride as the filling medium, a solid compound with phonon absorption bands at THz [19].…”

“…Surprisingly, an initially opaque metallic HA may become translucent with the incorporation of the molecular compound, at the spectral range where the molecules strongly absorb electromagnetic radiation. This phenomenon results: from the excitation of surface bounded waves when the molecules form a thin layer on top of the system [15,16]; and from the modification of the propagation constant of light inside the holes when the molecules can penetrate into them [11,16]. Waveguide and surface AIT operate simultaneously when the dye is present both in the holes and on the surface and are found close to the absorption energy of the molecules and exist separately one each other.…”

“…The AIT-based gas detector consists in a metallic hole array (HA), placed on top of a dielectric substrate (see Figure 2a) where the molecules to be detected are released in the air region, in contact with the HA (see Figure 2c). Our approach relies on the appearance of spectral features in transmission and reflection induced by the molecular specimen when this fills the holes [11], conversely to those approaches designed to feature strong resonances at the absorption energies of the molecules [12] and, with typical functionalities based on accurately measuring spectral shifts in the presence of a given substance [13]. To illustrate our proposal we have chosen the HCN gas as the substance to be detected in the air region.…”