Out-of-plane dispersion and homogenization in photonic crystal slabs
Click to view
(a) Power transmission coefficient and (b) relative phase for transmission perpendicular to the photonic crystal slab. The phase is measured relative to the case of no sample in the THz beam path. In (a), the solid line is the result of a FEM simulation, while in (b), the solid line is a FDTD simulation. Both simulations account for the finite thickness of the sample along the propagation direction, and both reproduce the frequency-dependent features of the data. The two insets show the transmission and relative phase for in-plane propagation (TM polarization), along the direction. The vertical dashed lines indicate the edges of the first (partial) photonic band gap. The slanted dashed line in (b) is a guide to the eye to indicate the linearity (and the zero intercept) of the in-plane phase at low frequencies.
Click to view
Effective refractive index vs frequency, for propagation normal to the plane of the photonic crystal slab, for the frequency range below the first guided resonance. The horizontal dashed line indicates the predicted homogeneous limit of , which is smaller than the measured low-frequency value of . The dotted curve shows the dispersion predicted by a band structure calculation for out-of-plane propagation, based on a plane wave method (see Ref. 16). The solid curve is the FDTD simulation from Fig. 1. In the inset, the equivalent result is displayed for propagation in the plane of the slab. In contrast to the out-of-plane result, the predicted homogeneous value of (horizontal dashed line) is precisely consistent with the measurement at low frequencies, . Deviations are observed only as the frequency approaches that of the band gap (vertical dashed lines).
Article metrics loading...
Full text loading...