Smallest possible electromagnetic mode volume in a dielectric cavity

Abstract
In photonic crystals, electromagnetic waves can be confined in all three dimensions – leading to very small mode volumes. A computational search has been made for the smallest electromagnetic mode volume which occurs in two-dimensional, dielectric photonic crystals slabs. The smallest mode volume found was V ≈ 2(λ/2n)3, where n is the refractive index. This small mode volume can lead to significant enhancement of spontaneous emission rates in semiconductor nano-cavities due to the Purcell effect.