Optical properties of point-defect nanocavity implemented in planar photonic crystal with various low refractive index cladding materials

This paper presents a theoretical investigation of the optical properties of a three missing holes point-defect cavity implemented in a planar photonic crystal with various low refractive index cladding materials. To describe the cavity operation, we analyze how the refractive index (RI) of the cladding material depends on the Q factor and resonant wavelength for both asymmetric and symmetric structures. The results show that the radiation losses of the structures increase for decreasing RI contrast and that the Q factor drops dramatically. We show that the periodicity of the RI of the cladding material is a critical consideration for realizing symmetric structures with high-Q factors. Furthermore, we fine-tune the radius and position of the lateral-, upper-, and lower-boundary holes near the cavity edges, which allows us to increase the Q factor of the planar photonic crystal cavity by a factor as large as 25 (Q > 104). These findings provide useful design rules for applications involving mechanically stable photonic crystal cavities with high-Q factors.