Enlargement of polarization-independent omnidirectional band gaps in the photonic heterostructures containing single-negative materials

We show that the frequency range of the zero effective phase gap in a photonic heterostructure containing single-negative materials can be enlarged owing to the property that its lower and upper frequency edges depend on the thickness ratio of the epsilon-negative and mu-negative materials. Compared to the zero effective phase gap of a single photonic crystal, the frequency range of the zero effective phase gap in a photonic heterostructure can be notably enlarged. Moreover, it is shown that the band edges of the zero effective phase gap is insensitive to incident angle and polarization of light.