All-angle negative refraction flatlens with a broad bandwidth

All-angle negative refraction (AANR) contributes to a subwavelength imaging with the ability to collect light from all incident angles to generate negative refraction. However, it is challenging to realize a broadband AANR with the conventional photonic crystal (PhC) structures due to the dispersion nature, which makes the refracted light highly sensitive to the incident angle. In this work broadband AANR PhCs are proposed based on the supercircle void or rod design, for transverse electric (TE) and transverse magnetic (TM) polarizations respectively. By adjusting the filling ratio of the dielectric material, the nearly optimal AANR range is realized. Flat lenses based on the supercircle designs are able to form subwavelength imaging in a frequency range 3 times broader than the state-of-the-art for TE polarization and 1.1 times for TM polarization, respectively.