Size Limits for Focusing of Two-Dimensional Photonic Quasicrystal Lenses

The circular main channels of a photon stream in a two-dimensional photonic quasicrystal lens are strictly defined. Both the critical state width range for unstable focusing and the width limit for stable focusing are deduced. Furthermore, the critical state width range and the width limit can be different for varying thicknesses of lens. A relationship between the wavelength of a point source and the minimum size of such lenses is proposed for double-photon-stream-beam interference focusing.