Geometric representation of adiabatic distributed-Bragg-reflectors and broadening the photonic bandgap

TL;DR

This paper draws an analogy between adiabatic population transfer in quantum systems and light propagation in photonic crystals, proposing a chirped distributed-Bragg-reflector to broaden the photonic bandgap and improve control over light transmission.

Contribution

It introduces a novel chirped DBR design inspired by quantum adiabatic techniques, enhancing the photonic bandgap and transmission control in classical optical systems.

Findings

Broadening of photonic bandgap observed

Suppression of sharp reflection peaks achieved

Adiabatic constraints satisfied via optimal chirping

Abstract

Adiabatic following has been an widely-employed technique for achieving near-complete population transfer in a `two-level' quantum mechanical system. The theoretical basis, however, could be generalized to a broad class of systems exhibiting SU(2) symmetry. In the present work, we present an analogy of population transfer dynamics of two level atomic system with that of light propagation in a classical `one-dimensional' photonic crystal, commonly known as distributed-Bragg-reflector (DBR). This formalism facilitates in adapting the idea of adiabatic following, more precisely the rapid adiabatic passage (RAP) which is usually encountered in a broad class of quantum-mechanical systems. We present a chirped DBR configuration in which the adiabatic constraints are satisfied by virtue of optimally chirping the DBR. The reflection spectrum of the configuration exhibit broadening of photonic bandgap (PBG) in addition to a varying degree of suppression of sharp reflection peaks in the transmission band. The intermodal coupling between counter-propagating modes as well as their phase-mismatch, for the DBR configuration, exhibits a longitudinal variation which is usually observed in `Allen-Eberly' scheme of adiabatic population transfer in two-level atomic systems.