Large-angle polarization insensitive negative refraction in the diagonal array photonic crystal

Abstract

In this article, the all-angle and polarization insensitive negative refraction (NR) properties are investigated in a 2D diagonal array photonic crystal. The rod-type structure presents the all-angle NR for TM2 in a bandwidth of Δω/ωc ∼ 20%. The all-angle NR does not hold for the hole-type structure due to the overlap of the 2nd and the 3rd bands, however, the polarization insensitive negative refraction is achieved for incidence angles of over θin = ±20° in a bandwidth of Δω/ωc = 10.6% in the second band. The proposed structure has been investigated using the PWE and the FDTD methods, regarding fabrication challenges in Si technology for the central operating wavelength of λc = 1550 nm.