“…However, when an atom is located at some unusual electromagnetic environment instead of free space, the spontaneous emission can be modified. For example, the spontaneous emission can be enhanced or inhibited in a cavity [22][23][24][25][26][27] and it can also be modified in photonic crystals [13][14][15][16][17]20,21,[28][29][30][31][32][33][34] or in left-hand materials [18,19]. What is more, when an atom is embedded in a linear dielectric, the atomic spontaneous decay can also be modified [35][36][37][38][39].…”