Limitations on bandwidth-integrated passive cloaking

TL;DR

This paper develops a framework to determine fundamental limits on the bandwidth and performance of passive cloaks, revealing that perfect cloaking over any finite bandwidth is impossible due to physical constraints.

Contribution

The authors introduce a general method to compute structure-agnostic bounds on passive cloaking performance across bandwidths, applicable to 2D circular objects.

Findings

Perfect cloaking cannot be achieved over any finite bandwidth.

Bounds scale linearly with bandwidth, material loss, and inverse of the cloak's radial thickness.

Finite size and material loss impose fundamental performance limits.

Abstract

We present a general framework for the computation of structure-agnostic bounds on the performance of passive cloaks over a nonzero bandwidth. We apply this framework in 2D to the canonical scenario of cloaking a circular object. We find that perfect cloaking using a finite-sized isotropic cloak is impossible over any bandwidth, with the bounds scaling linearly with the bandwidth before saturating due to the finite size of the cloak and the presence of material loss. The bounds also exhibit linear scaling with material loss in the cloak and linear scaling with the inverse of the radial thickness of the design region before saturation due to finite-size effects or the presence of material loss. The formulation could readily find applications in the development of cloaking devices, setting expectations and benchmarks for optimal performance.