Coherent perfect absorption in wedged organic thin films: a method to determine optical properties

We investigate coherent perfect absorption in layered thin-film structures with organic small molecules as absorbing material. We focus on strongly asymmetric resonator structures, realized with a high-optical-quality dielectric-distributed Bragg reflector and a thermally evaporated wedged organic layer on top. The optical properties of these devices are systematically investigated by selective optical pumping and probing of the structure along the wedge. We show that phases and amplitudes of all waves and their balance relations can be tuned such that coherent perfect absorption is achieved, i.e., almost all incident radiation is absorbed within the thin organic layer. We show that such wedged structures on highly reflective dielectric mirrors can be used as a novel approach to measure optical dispersion relations of absorbing materials in a broad spectral range without requiring any specific a priori knowledge of the absorbing film.