1. non-hermitian degeneracies of optical modes in non-integrable dielectric microdisks

Changhwan Yi

DGIST, Korea

10 December 2020 Thu 4 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

Realistic physical systems are never able to be isolated from their environment. Thus, strictly speaking, they should be treated as open systems. Because of this openness, energy levels are given in terms of non-Hermitian operators instead of traditional energy conserved Hermitian Hamiltonian. Here, there are special degeneracies called “exceptional points” (EPs) in the parametrically controllable open quantum (wave) systems, at which not only the energy levels (resonant frequencies) but also the corresponding eigenstates (modes) coalesce.

Meanwhile, there is another inevitable feature of realistic physical systems; that is, a nonintegrability arisen owing to the impossibility of perfect symmetries in nature. Finding the underlying principles associated with this property is the main agenda of quantum chaos. One outstanding accomplishment in this field can be referred to as a theory of dynamical tunneling, which tackles non-energetic barriers in phase space. Among several different classes of dynamical tunneling, our major interest is in the so-called “resonance assisted tunneling” (RAT), which can efficiently describe mode interactions in near-integrable systems.

Providing fundamental introductions of general optical microcavity-related topics, the primary emphasis of this talk is on the demonstration of the explicit role of RAT in the emergence of EPs coalescing the so-called "internal-modes." In addition, we show that a relatively unfamiliar class of modes, the so-called “external modes,” can also exhibit an exceptional point through a coupling with the internal modes as well.