Variation of spontaneous emission in the opal stop-band with an enhanced refractive-index contrast

Abstract

Photoluminescence spectra of an opal with an anatase layer grown on its inner surface were studied. Measurements were carried out with a high angular resolution at various pump power levels and detection angles. The intensity and probability of emission were found to acquire an anisotropy corresponding to the frequency and angular dispersion of the first opal photonic band gap. As the pump power increases, the suppression of spontaneous emission in the photonic band gap is shown to be replaced by its amplification. The amplification of spontaneous emission is tentatively assigned to the existence of localized defect optical modes in the photonic band gap.