Two mechanisms of disorder-induced localization in photonic-crystal waveguides

TL;DR

This paper investigates how fabrication imperfections cause light localization in photonic-crystal waveguides, revealing two distinct regimes linked to the density of states and photon effective mass, with insights from simulations and experiments.

Contribution

It identifies and characterizes two different disorder-induced localization regimes in photonic-crystal waveguides through numerical and experimental methods.

Findings

Two localization regimes linked to density of states and photon effective mass.

Localization length can be tuned by adjusting lattice parameters.

Experimental verification using quantum dot photoluminescence.

Abstract

Unintentional but unavoidable fabrication imperfections in state-of-the-art photonic-crystal waveguides lead to the spontaneous formation of Anderson-localized modes thereby limiting slowlight propagation and its potential applications. On the other hand, disorder-induced cavities offer an approach to cavity-quantum electrodynamics and random lasing at the nanoscale. The key statistical parameter governing the disorder effects is the localization length, which together with the waveguide length determines the statistical transport of light through the waveguide. In a disordered photonic-crystal waveguide, the localization length is highly dispersive, and therefore, by controlling the underlying lattice parameters, it is possible to tune the localization of the mode. In the present work, we study the localization length in a disordered photonic-crystal waveguide using numerical simulations. We demonstrate two different localization regimes in the dispersion diagram where the localization length is linked to the density of states and the photon effective mass, respectively. The two different localization regimes are identified in experiments by recording the photoluminescence from quantum dots embedded in photonic-crystal waveguides.