Parity-time symmetry and coherent perfect absorption in a cooperative atom response

Nanophotonics

article

Kyle E. Ballantine¹  Janne Ruostekoski¹ 

[1] Department of Physics, Lancaster University

关键词: cold atoms;    cooperative response;    exceptional points;    metasurfaces;    optical lattices;    PT symmetry;   

DOI  :  10.1515/nanoph-2020-0635

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

Parity-Time (PT$\mathcal{P}\mathcal{T}$) symmetry has become an important concept in the design of synthetic optical materials, with exotic functionalities such as unidirectional transport and nonreciprocal reflection. At exceptional points, this symmetry is spontaneously broken, and solutions transition from those with conserved intensity to exponential growth or decay. Here, we analyze a quantum-photonic surface formed by a single layer of atoms in an array with light mediating strong cooperative many-body interactions. We show how delocalized collective excitation eigenmodes can exhibit an effective PT$\mathcal{P}\mathcal{T}$ symmetry and nonexponential decay. This effective symmetry is achieved in a passive system without gain by balancing the scattering of a bright mode with the loss from a subradiant dark mode. These modes coalesce at exceptional points, evidenced by the emergence of coherent perfect absorption where coherent incoming light is perfectly absorbed and scattered only incoherently. We also show how PT$\mathcal{P}\mathcal{T}$ symmetry can be generated in total reflection and by balancing scattering and loss between different polarizations of collective modes.

【 授权许可】

CC BY