Polarization-insensitive, wide-angle broadband perfect absorber with patch structures

We present a polarization-insensitive, wide-angle broadband perfect absorber with planar patch structures. The finite difference time domain method, transfer matrix method, and effective medium theory are applied for the design and analysis of the perfect absorber. Titanium nitride (TiN) and indium tin oxide (ITO) are introduced as the layers and planar patch structures. The unit cell structure is mainly composed of a pair of TiN/ITO layers and four planar patches as the top layer. The average absorption is higher than 95% between the wavelengths of 550 and 1100 nm. The average absorption remains above 90% between 500 nm and 1100 nm with a wide range of incident angles from 0 degrees to 60 degrees. The electrical field intensity distributions are calculated to understand the broadband absorption mechanism. The designed broadband absorber could be very promising for application in solar thermal energy harvesting and photo detection devices.