Penetration depth in near-field radiative heat transfer between metamaterials

In this letter, we investigate the penetration depth in near-field radiative heat transfer between metamaterials when surface polaritons are excited at both electrical and magnetic resonances. The analyses show that based on the optical properties of the metamaterial, two different penetration depths can be defined corresponding to electrical and magnetic resonances. Depending upon the scattering rate of the metamaterial, it is possible to selectively enhance or reduce the penetration depth of near-field thermal radiation at electric and magnetic resonances. The results obtained from this study will benefit applications of metamaterials in near-field energy harvesting.