Coherent Perfect Absorption In Resonant Materials

Coherent perfect absorption (CPA) is an interferometric effect that guarantees full absorption in a lossy layer independently of its intrinsic losses. To date, it has been observed only at a single wavelength or over narrow bandwidths, whereupon wavelength-dependent absorption can be ignored. Here we produce CPA over a bandwidth of similar to 60 nm in a 2 mu m thick polymer film with a low-doping concentration of an organic laser dye. A planar cavity is designed with a spectral 'dip' to accommodate the dye resonant linewidth, and CPA is thus achieved even at its absorption edges. This approach allows realizing strong absorption in laser dyes-and resonant materials in general-independently of the intrinsic absorption levels, with a flat spectral profile and without suffering absorption quenching due to high doping levels.