Coherent perfect absorption in artificially engineered nanometer metal/semiconductor composite films at oblique incidence

We show theoretically and numerically that artificially engineered nanometer metal/semiconductor composite films provide a versatile platform for coherent perfect absorption (CPA) of light. By engineering the effective permittivity of the composite nanofilms and tailoring the angle of incidence, CPA can be realized freely in a wide range from visible to infrared. A proof-of-principle demonstration using Au/Ge composite nanofilms is implemented. The results show that CPA can be achieved at any wavelength within the studied range. By contrast, CPA cannot be achieved for single layer of Au or Ge with the same thickness. The simple approach to obtain CPA provides a great deal of flexibility in selecting absorption materials, preparation technology, illumination configuration, and wavelength range. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement