Transmission spectra changes produced by decreasing compactness of opal-like structures

Abstract

Artificial opal-like structures based on spheres and colloidal particles have been fabricated in a controlled way, presenting optical band-gap properties in the optical frequency range. Nonclose packed artificial opals have also been fabricated and studied recently. In order to gain a better understanding of these phenomena, we have studied macroscopic models of nonclose packed fcc lattices using glass spheres (ε=7) of 8 mm diameter, and measuring in the microwave region (from 10 to 30 GHz). The results have shown a Bragg resonance tunable with filling factor of the opal, and a strong rejected band similar, also present in close packed samples, much less affected by compactness. The relation of this high order band with spheres single layer behavior is also discussed.

Photonic band effects in three dimensional lattices of macroscopic-sized dielectric spheres derived from microwave transmission spectroscopy

“…The existence of a pseudo gap can be observed as a lack of transparency in transmission spectra; however, the contrary is not true, some peaks in transmission spectra are not generated by band gaps. Higher energy rejected bands (called sometimes "high order bands") have been reported and discussed (Miguez et al 2004;Gastón et al 2005;Vlasov and Norris 2001;Norris and Vlasov 2001;Miguez 2000;Galisteo-López and López 2004;García-Santamaría et al 2007;Andueza et al 2009), but their physical origin still remains unclear.…”

Design of optical filters based on the compactness of 2D-arrays of dielectric spheres

“…In the same way, studies regarding the effect of compacting in the electromagnetic transmission of dielectric spheres monolayers [7]; or the frequency variations in the resonant modes of a single layer of spheres with its compactness [5], or even the absorption properties of dielectric spheres (glass) monolayers in the microwave domain [8]. The behaviour of single layered dielectric spheres arranged in square and triangular geometries was described in [9]; as well as the transmission spectra changes produced by decreasing compactness [10].…”