Spectrally selective mid-infrared absorber/emitter by controlling optical Tamm states with thin phononic film

Abstract We demonstrate the near-unity absorption of multilayer structures in the mid-infrared (MIR). The first configuration consists of a distributed Bragg reflector and a subwavelength-thin phononic film on top. Optical waves are confined within the cavity and the interface of the top layer, resulting in narrowband selective perfect absorption at the wavelength of 12.56 μm, which is of particular interest for many technological applications. Thus, highly spectral selective thermal emission can emerge from the engineered phononic-photonic structure. Tamm absorber can also be realized when the light from the phononic film side is perfectly absorbed. Reflectance of the fabricated sample is measured using a Fourier transform infrared spectrometer (FTIR) and matches the simulations well. Our findings will pave a new avenue for harness surface phonon (SPh) modes in the MIR, which could benefit applications such as radiative cooling, selective thermal emission and MIR sensing.