| Abstract: | Rabi oscillations are well known from quantum mechanics, where a two-state system is driven periodically by an electromagnetic field and undergoes periodic population exchanges. Recently, Rabi oscillation were proposed .and demonstrated in photonics lattices in the paraxial regime. However, recent technological progress makes it possible to fabricate waveguide structures narrower than the optical wavelength. In such structures, neither the paraxial approximation nor the scalar Helmholtz equation is valid, and the dynamics must to be analyzed through the full Maxwell equations. In this seminar I will presents our study on Rabi oscillations between optical Bloch-modes in waveguide arrays of sub-wavelength periodicity. We show that, in this realization the Rabi frequency and of the electric field of the light diverge, as the transition approaches a unique point (known as “exceptional point”, EP) at which one of the optical Bloch-modes becomes self-orthogonal. This unusual behavior arises from the structure of Maxwell’s equations, which can give rise to a mathematical EP when the field varies rapidly at sub-wavelength scale. This study demonstrate that small changes in the optical wavelength can dramatically affect the propagation dynamics, offering an effective tool for light manipulation in nano-structures, and can be used to switch on/off nonlinear effects in a selective fashion. |
