Optical surface resonance may render photonic crystals ineffective

Abstract

In this work we identify and study the presence of extremely intense surface resonances that frustrate the coupling of photons into a photonic crystal over crucial energy ranges. The practical utility of photonic crystals demands the capability to exchange photons with the external medium, therefore, it is essential to understand the cause of these surface resonances and a route to their elimination. We demonstrate that by modifying the surface geometry it is possible to tune the optical response or eliminate the resonances to enable full exploitation of the photonic crystal.

Tailoring the Electrical Properties of Inverse Silicon Opals ‐ A Step Towards Optically Amplified Silicon Solar Cells

“…[11][12][13] In particular, the inverse silicon opal (i-Si-o) with a high refractive-index contrast has attracted attention because of its demonstrated complete photonic band gap at 1.5 mm and the possibility of large-scale synthesis.[14] While the optical properties of i-Si-o have been thoroughly investigated, [15,16] little research has been focused on its electrical behaviour, knowledge that would underpin the development of any kind of electro-optical device based on i-Si-o. It can be envisioned that the electrical properties of i-Si-o with its 3D open-framework microstructure could be very different from that of Si thin films, similar to the different behaviour observed for electrochemically etched porous silicon.…”

Organic dye-sensitized sponge-like TiO 2 photoanode for dye-sensitized solar cells

“…The low-magnification planar view indicates that the upper surface of the TiO 2 sample is very smooth, and that there is a thin overlayer on top of the hierarchical porous structure because of the excess of the TiO 2 precursor (TiBALDH) in the mixed assembling solutions [32]. The surface overlayer may render the photons incident onto the interface of the overlayer and scatter them back into the interior of the photoanode and therefore enhance the light absorbance of the dye attached to TiO 2 [33,34]. From the high-magnification planar view in figure 1b, the granular morphology can be clearly observed, and several pores derived from the colloidal sphere templating are also easily recognized.…”

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.…”