Smallest possible electromagnetic mode volume in a dielectric cavity

In photonic crystals, electromagnetic waves can be confined in all three di mensions leading to very small mode volumes, a computational search has bee n made for the smallest electromagnetic mode volume which occurs in two-dim ensional. dielectric photonic crystals slabs. The smallest mode volume foun d was V approximate to 2(lambda/2n)(3), where n is the refractive index. Th is small mode volume can lead to significant enhancement of spontaneous emi ssion rates in semiconductor nano-cavities due to the Purcell effect.