Programme

I.13 -- Invited, VCTP-46

Date: Wednesday, 6 October 2021

Time: 17:00 - 17:30

The exceptional properties of non-Hermitian photonics with subwavelength optical lattices

Hai Son Nguyen

Institut des Nanotechnologies de Lyon, Ecole Centrale de Lyon, 69130 Écully, France

The maturity of nanophotonics in both nanofabrications and theoretical conceptions provides a versatile platform to study open quantum system with custom-cut gain and losses mechanisms. Interestingly, while rigorous quantum formalismfor open systems replaces Hermitian Hamiltonians of Schrödinger equation by Liovillian supeoperators for the density matrix, non-conservative photonic systems can be nicelydescribed by non-Hermitian Hamiltonians. As consequences, the eigenstates of the system are quasinormal modes with complex eigenvalues. This leads to intriguing features such as Exceptional Points (EPs) at which both eigenstates and eigenvalues coalescence simultaneously, and Bound State In the Continuum (BICs) due to destructive quantum interference.
In this presentation, I will first introduce the non-Hermitian Hamiltonian formalism with a 2x2 toy model example. Then I will show how to engineer such a Hamiltonian with photonic platform, making use of subwavelength scale photonic crystal. The experimental observation of BICs and EPs will be described in detail. Finally, we will discuss on the topological nature of our non-Hermitian system (polarization singularities, band inversion of non-Hermtian band structures, non-Hermitian winding numbers).
References:
1. Bound states in the continuum, Nature Reviews Materials, 1, 16048 (2016) (DOI: 10.1038/natrevmats.2016.48)
2. Exceptional points in optics and photonics, Science, 363, 6422, eaar7709 (2019) (DOI: 10.1126/science.aar7709 )

Presenter: Nguyen Hai Son