Bloch harmonics and focusing properties in the photonic crystal planoconcave lens structure

摘要: Focusing properties of a plane wave by the photonic crystal (PC) concave lens placed in air environment are studied through finite-difference time-domain technique. The PC works frequency window located second transversal electric (TE)-polarized band. A good-quality focus can form out planoconcave lens, while is also formed for point source at consistent with analysis band structure and equifrequency contours. Besides plane-wave expansion method, we analyze Bloch harmonics inside region Fourier method. It shown that mode, which consists more than one spatial frequency, contributes to focus. results show frequencies Brillouin zone mainly generated due periodic potential arising from or existence interfaces.