Spontaneous emission from a double V-type four-level atom in a double-band photonic crystal

Quantum interferences in spontaneous emission from a double V-type four-level atom in a double-band photonic crystal have been investigated. The double V-type transitions from the two upper levels to the two lower levels can interact not only with modes near the edges of a double-band photonic band gap, but also with free vacuum modes. The resulting two types of quantum interferences give rise to not only dark lines, but also a narrow spontaneous line in the spectrum from the transition coupled to the free vacuum modes. The dark lines and narrow spontaneous line are shown to be dependent on the width of the forbidden gap, relative position of the upper levels from the band edges, coupling constants, and initial coherent superposition state of the system.