Generalized parametric Space, parity symmetry of reflectance, and optical forces for parity time symmetric photonics
Jeng Yi Lee1*, Pai-Yen Chen2
1Department of Opto-Electronic Engineering, National Dong Hwa University, Hualien, Taiwan
2Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, USA
* Presenter:Jeng Yi Lee,
Photonic systems can be regarded as parity time symmetry when its optical indexes of refraction in spatial displacement can satisfy n(r)=n(-r), i.e., a delicate balance of gain and loss. Over past decades, PT-symmetric systems can exhibit coherent perfect absorption- lasing, unidirectional invisibility, power oscillation, Bloch oscillation, and negative refraction. In this presentation, with Lorentz reciprocity theorem, we develop a generalized parametric space to indicate symmetry phase, exceptional point, broken-symmetry phase, anomalous scattering events, reflectance, and transmittance [1]. We find the parity symmetry of reflection, even PT-symmetric system violates spatial parity alone. The bi-directional reflection-less can be occurred at the exceptional point. Interestingly, PT-symmetric system operating at this exceptional point can possess any transmission phases. With the generalized parametric space, we also discuss the optical forces from two individually opposite illumination. We find that in the symmetry phase, the optical forces are always pushing and asymmetry. In the exceptional point, the optical force can be null or pushing, depending on the illumination direction, that has the potential application in force rectifiers. In the broken symmetry phase, the optical force can be bi-directional null, pushing, and pulling [2]. Our discussion goes beyond any specific PT-symmetric system configurations and materials embedded.

[1] Jeng Yi Lee and Pai-Yen Chen, ''Generalized parametric space, parity symmetry of reflection, and systematic design approach for parity-time-symmetric photonic systems,'' Phys. Rev. A 104, 033510 (2021)
[2] Jeng Yi Lee and Pai-Yen Chen, "Optical symmetric pushing, uni-/bi-directional null, and pulling-pushing flipped forces in one dimensional PT-symmetric photonics," (2021)

Keywords: Parity time symmetric (PT) photonics, PT symmetry phase, exceptional point, broken-symmetry phase, coherent perfect absorption- lasing, unidirectional invisibility