Spontaneous emission in a three-level atom is investigated inside a dielect
ric cavity between asymmetrically photonic crystals. The photonic crystals
are treated within the effective medium approach and the modes dispersions
and field amplitudes are determined. The atomic probability amplitudes and
spontaneous emission spectra are evaluated for different atomic and cavity
parameters. The probability amplitudes show interference effects due to spo
ntaneous emissions from the upper levels to the lower level. Interesting fe
atures arise for the variations of the probability amplitudes and spontaneo
us emission spectra with the variations of frequency near the photonic crys
tals including dark lines and multi-peaks.