Abstract
The effective medium approach was applied to a dielectric slab between one-dimensional photonic crystals and the dispersion curves together with the field amplitudes were determined. The probability amplitude and the spontaneous emission spectrum were investigated for a two-level atom immersed in the region between the photonic crystals. The spontaneous emission rate was calculated numerically and an interesting feature is that this rate is zero for certain slab thicknesses. The probability amplitude and the spontaneous spectrum show peaks and dips when the mode frequency approaches the photonic gap regions.