Tuning Optical Absorption in an Ultrathin Lossy Film by Use of a Metallic Metamaterial Mirror

We present a way to tune the spectral light absorption properties of an ultrathin planar superabsorbing semiconductor film placed on a metallic metamaterial mirror. It is shown that we can change the wavelength of maximum absorption in a lossy film with a fixed thickness by tailoring the filling ratio of the metallic metamaterial. This remarkable ability of tuning originates from the control of the reflection phase pickup of light impinging from the lossy film upon the metallic metamaterial mirror. Full-field electromagnetic simulations show good agreement with the theoretical predictions. The proposed approach allows for a convenient and highly controllable way to achieve spatially variant tuning of absorption in a semiconductor film.