Absorption in metamaterials : feasibility of device applications.

We dispel some of the myth around the emerging metamaterials as to their feasibility for device applications. In particular, we study a delay device based on resonant tunneling (RT) through a layered structure with a negative index medium(NIM) slab as a constituent layer. We demonstrate significant delays in RT via the plasmonic and guided modes. We retain both the sources of dispersion (namely, structural and intrinsic,) along with absorption for a recently reported realistic NIM. We show how the damping in recent metamaterials can kill the RT effects. Our studies reiterate Veselago’s observation on the absolute necessity of retaining dispersion in metamaterials related studies. 

Despite the destruction of RT transmission features, there can still be interesting and useful applications for the broadband absorption of NIMs, albeit in a non-standard frequency domain. Broadband omnidirectional reflectivity was demonstrated recently for realistic NIM slabs [Bloemer et al, Appl. Phys. Lett. 87,261921(2005)]. We study a system of two such NIM slabs coupled through a dielectric spacer layer and show that the structure can lead to critical coupling resulting in null scattering. In other words, at specified frequencies or pairs of frequencies, the system can absorb all the incident energy without any reflection or transmission. We demonstrate continuous and discrete tunability of the critical coupling frequencies by varying the angle of incidence. Such structures can find applications in quantum information processing where there is a need to absorb the remnant stray photons.