Abstract

PT-symmetric structures, such as a pair of coupled waveguides with balanced loss/gain, exhibit a singularity of their eigenvalues around an exceptional point, hence a large apparent differential gain. In the case of fixed losses and variable gain, typical of plasmonic systems, a similar behavior emerges but the singularity is smoothened, especially in more confined structures. This reduces the differential gain around the singular point. Our analysis ascribes the origin of this behavior to a complex coupling between the waveguides once gain is present in an unsymmetrical fashion, even if guides feature the same modal gains in isolation. We demonstrate that adjunction of a real index variation to the variable waveguide heals the singularity nearly perfectly, as it restores real coupling. We illustrate the success of the approach with two geometries, planar or channel, and with different underlying physics, namely dielectric or plasmonic.

© 2012 IEEE

Implementation of PT symmetric devices using plasmonics: principle and applications

Henri Benisty, Aloyse Degiron, Anatole Lupu, André De Lustrac, Sébastien Chénais, Sébastien Forget, Mondher Besbes, Grégory Barbillon, Aurélien Bruyant, Sylvain Blaize, and Gilles Lérondel
Opt. Express 19(19) 18004-18019 (2011)

Switching using PT symmetry in plasmonic systems: positive role of the losses

Anatole Lupu, Henri Benisty, and Aloyse Degiron
Opt. Express 21(18) 21651-21668 (2013)

Switching between singular points in non-PT-symmetric multilayer structures using phase-change materials

Yin Huang, Lanyan Wang, Yuecheng Shen, and Georgios Veronis
Opt. Express 29(1) 454-469 (2021)

Singular properties generated by finite periodic PT-symmetric optical waveguide network

Jian Zheng, Xiangbo Yang, Dongmei Deng, and Hongzhan Liu
Opt. Express 27(2) 1538-1552 (2019)

Optical gradient forces in PT-symmetric coupled-waveguide structures

Xinbiao Xu, Lei Shi, Linhao Ren, and Xinliang Zhang
Opt. Express 26(8) 10220-10229 (2018)