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Chapitre D'ouvrage Année : 2021

22 - Superluminal, Negative Delay Times and Selective Transmission in Isotropic-Anisotropic Layered Media

Résumé

In this chapter, we investigate the possibility of superluminal and negative delay times for electromagnetic wave propagation in a linear and passive periodic structure consisting of alternating isotropic and anisotropic media. These phenomena are due to the birefringence of the anisotropic layers of the structure. By adjusting the orientations of these layers, the delay times of transmitted waves can be controlled from subluminality to superluminality, and vice versa. Numerical results indicate that the apparent superluminal propagation of light occurs inside the photonic bandgaps when the principal axes of the anisotropic layers are parallel or perpendicular to the fixed axes. For other orientations of these layers, tunneling and superluminal regimes appear inside the photonic bandgaps (PBG) and in the allowed bands for frequencies close to the transmission minima. The effect of the number of unit cells of the photonic crystal (PC) structure on the propagation of light with superluminal and negative delay times is also investigated. We show that the structure exhibits the Hartman effect in which the tunneling delay time of electromagnetic wave through the PBG of the structure converges asymptotically to a finite value with increasing the number of layers. The control of the magnitude and the sign of the delay time of light propagation represent a key point in slow and fast light technologies. Also, we investigate theoretically the possibility to control the optical transmission in the visible and infrared regions by introducing a defect anisotropic layer in a finite isotropic PC. We evaluate the delay times of the localized modes and compare their behavior with the total density of states (DOS). We show that the birefringence of an anisotropic defect layer has a significant impact on the behavior of the optical modes in the electromagnetic forbidden bands of the structure. The amplitudes of the defect modes in the transmission and the delay time spectrum, depend strongly on the position of the cavity layer within the photonic crystal. The anisotropic defect layer induces transmission zeros in one of the two components of the transmission as a consequence of a destructive interference of the two polarized waves within this layer, giving rise to negative delay times for some wavelengths in the visible and infrared light ranges. The proposed structures in this chapter represent new systems for controlling the delay times of wave propagation without a need of active or nonlinear media, as well as lossy or asymmetric periodic structures. Also, they offer several possibilities for controlling the frequencies, transmitted intensities, and delay times of the optical modes in the visible and infrared regions and can be good candidates for realizing high-precision optical filters. The Green's function approach has been used to derive the transmission and reflection coefficients, the density of states (DOS), as well as the delay times of optical waves propagating through these structures.

Dates et versions

hal-03360015 , version 1 (30-09-2021)

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El Houssaine El Boudouti, Bahram Djafari-Rouhani, Abdellatif Akjouj, L. Dobrzynski. 22 - Superluminal, Negative Delay Times and Selective Transmission in Isotropic-Anisotropic Layered Media. Photonics, Part Three: Photonic Materials, Elsevier, pp.623-655, 2021, 978-0-12-819388-4. ⟨10.1016/B978-0-12-819388-4.00033-2⟩. ⟨hal-03360015⟩
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