Search

We introduce a class of non-Hermitian systems that break electromagnetic reciprocity while preserving time-reversal symmetry, and describe its novel polarization dynamics. We show that this class of systems can be realized using van der Waals heterostructures involving transition-metal dichalcogenides (TMDs). Our work provides a path towards achieving strong optical nonreciprocity and polarization-dependent directional amplification using compact, large-area and magnet-free structures. [ABSTRACT FROM AUTHOR]

We develop theoretical and computational formalisms to describe thermal radiation from temporally modulated systems. We show that such a modulation results in a photon-based active cooling mechanism. This mechanism has a high thermodynamic performance that can approach the Carnot limit. Our work points to exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications. [ABSTRACT FROM AUTHOR]

We develop a theory of solar cell light trapping based on directly solving Maxwell's equations through a nonequilibrium Green's function formalism. This theory rigorously connects the maximum power absorbed by the solar cell to the density of states of the cell. With this theory we are able to reproduce all standard results in solar cell light trapping previously derived using approximate formalisms. Therefore our development places solar cell light trapping theory on a much firmer theoretical foundation. Moreover, here the maximum power formula is derived without the assumption of reciprocity, unlike previous theories on solar cell light trapping. Therefore, we prove that the upper bound of light trapping enhancement cannot be overcome with the use of nonreciprocal structures. As a numerical test, we simulate an absorber structure that consists of a nonreciprocal material, and show that the absorption enhancement factor is largely independent of nonreciprocity, in consistency with the theory. [ABSTRACT FROM AUTHOR]