Higher order Bragg diffraction by strongly photonic fcc crystals: onset ofa photonic bandgap

Citation
Wl. Vos et Hm. Van Driel, Higher order Bragg diffraction by strongly photonic fcc crystals: onset ofa photonic bandgap, PHYS LETT A, 272(1-2), 2000, pp. 101-106
Citations number
26
Categorie Soggetti
Physics
Journal title
PHYSICS LETTERS A
ISSN journal
03759601 → ACNP
Volume
272
Issue
1-2
Year of publication
2000
Pages
101 - 106
Database
ISI
SICI code
0375-9601(20000717)272:1-2<101:HOBDBS>2.0.ZU;2-K
Abstract
We have measured angle-resolved reflectivity of fcc photonic crystals made of air spheres in titania (TiO2), with lattice constants between 830 and 86 0 nm, that strongly interact with light. At normal incidence, we observe th ree new Bragg peaks at frequencies of 14800, 16700 and 18100 cm(-1) in the range of 2nd order diffraction. The peak frequencies have negligible disper sion over more than 30 degrees angular range, unlike usual Bragg diffractio n. The number, center frequencies and angular range of the peaks agree well with stop gaps in photonic bandstructures, computed for a model wherein th e TiO2 is distributed in shells about close-packed and interconnected air s pheres. It appears that higher-order Bragg diffraction in strongly photonic crystals is caused by a complex coupling of many Bloch waves that results in dispersionless bands. The computed stop gaps persist for stronger photon ic crystals with larger filling fraction or increased dielectric contrast. The 16700 cm(-1) peak is the precursor of a complete photonic band gap. (C) 2000 Elsevier Science B.V. All rights reserved.