Analysis of light propagation in index-tunable photonic crystals

Abstract

Propagation behaviors of light in index-tunable photonic crystals were analyzed by calculating the directions of the group velocity of light in the photonic crystals. Simulation results reveal that the band structures of tunable photonic crystals are highly anisotropic and the equifrequency surface curves in the wave-vector space of photonic crystals can show acute variation corresponding to an index change when operation frequency and incident angle are carefully selected. In the case of a triangular system composed of ferroelectric background and circular airholes, “on/off” switching can be operated when operation frequency a/λ is 0.4205 and the incident angle falls into a window of 32°–49°. Light can deflect 40° when the operation frequency a/λ and incident angle are 0.5372 and 23°, respectively. Two types of optical switches based on the anisotropic characteristics of index-tunable photonic crystals are proposed, which will find great potential applications in optical communications.

Fabrication of Ferroelectric Photonic Crystals

“…If the refractive index is 2.3, an electric field of 97 kV/cm may cause 1%-decrease in refractive index. This means that an applied voltage of 9.7 V to the 1 µm-thick PLZT photonic crystals will cause 40 • -swinging of light with a wavelength of 1.55 µm according to Xiong's calculation [12]. Figure 7 shows a fabricated PLZT photonic crystal.…”

“…Recently, Xiong et al proposed the design of a two dimensional indextunable photonic crystal [12]. They expect that 1%-decrese in refractive index can swing the light with a wavelength of 1.55 µm by 40 • in the photonic crystals consisted of (Pb,La)(Zr,Ti)O 3 (PLZT) matrix and 800 nm-pitch airholes with a diameter of 560 nm.…”

The beam splitting in the photonic crystal at a degenerate state

“…3 shows the PC equi-frequency contours (EFCs) of the second photonic band in the Brillouin zone. In order to realize the wavelength sensitivity selection, the wavevector of the air should reach the air EFC inside of the drastic high symmetry region labeled by the red circle [9,10]. Take normalized frequency ω = 0.613 for example, shown in Fig.…”

Tunable photonic crystal structures

“…7 These materials may be nonlinear materials, such as, liquid crystals (LC), or conventional electro-optic materials such as lead lanthanum zirconate titanate (PLZT) in which an index change of 0.12 can be achieved and switched at gigahertz speeds. 14,15 For the practical implementation of these concepts, it was assumed that the top electrodes were linearly patterned to align along one side of the triangular lattice and the bottom electrode was either un-patterned and covered the entire slab, or consisted of linear electrodes oriented parallel to the top electrode structure. As shown in Figure 2, the top electrodes separately bias alternate rows of holes to produce an additional periodicity in refractive index along a direction perpendicular to the top electrodes (one of the Γ-M directions in the reciprocal lattice of the triangular lattice) and thereby creates a superlattice PC.…”