Control of spontaneous emission from a laser-driven four-level atom in photonic crystals

We study the steady-state behaviour of spontaneous emission of a driven four-level atom embedded in photonic crystals. Considering different initial conditions, we discuss the influence of photonic band gap and detuning of external driving field on the atomic spontaneous emission spectrum. The photonic band gap and external driving field will impact strongly on the atomic spontaneous emission properties. Some interesting phenomena were found such as laser-induced dark line, laser-induced spectral-line narrowing and laser-induced pushing of a dressed state out of the band gap, which can be attributed to the quantum interference effect and control of the external driving field.