Experimental demonstration of complete photonic band gap in two-dimensional photonic crystal slabs

The realization of a photonic band gap (PBG)—not only for transverse electric (TE), but also transverse magnetic (TM)-like polarization modes in two-dimensional photonic crystal slab—is of interest for various applications. Such a complete PBG has been investigated theoretically in two-dimensional structures of which thickness is infinity. However, a complete PBG has not been demonstrated in feasible two-dimensional slab structure. In this letter, we propose two-dimensional photonic crystal slabs consisting of a triangular lattice of triangular air holes to achieve a complete PBG, and report the transmission spectra of fabricated samples. The results indicate that the degeneracy between the first and second band at the J point for TM-like polarization mode is solved, and PBG for TM-like polarization mode is obtained. Finally, we confirm the overlap of PBG between TE- and TM-like polarization modes.