Rainbow Trapping in a Chirped Three-Dimensional Photonic Crystal

TL;DR

This paper demonstrates theoretically and experimentally how a chirped three-dimensional photonic crystal can localize and enhance light at specific positions, leading to significant intensity amplification and potential applications in light-matter interactions.

Contribution

It introduces a novel 3D photonic crystal design with a gradual interlayer variation that achieves broadband light trapping and localization, surpassing previous 1D and 2D configurations.

Findings

Light localization and intensity enhancement confirmed experimentally.

Localization is chromatically resolved, with different frequencies stopped at different positions.

Potential for over two orders of magnitude increase in light-matter interaction enhancement.

Abstract

Light localization and intensity enhancement in a woodpile layer-by-layer photonic crystal, whose interlayer distance along the propagation direction is gradually varied, has been theoretically predicted and experimentally demonstrated. The phenomenon is shown to be related to the progressive slowing down and stopping of the incoming wave, as a result of the gradual variation of the local dispersion. The light localization is chromatically resolved, since every frequency component is stopped and reflected back at different spatial positions. It has been further discussed that the peculiar relation between the stopping distance and the wave vector distribution can substantially increase the enhancement factor to more than two orders of magnitude. Compared to previously reported one- and two-dimensional photonic crystal configurations, the proposed scheme has the advantage of reducing the propagation losses by providing a three-dimensional photonic bandgap confinement in all directions. The slowing down and localization of waves inside photonic media can be exploited in many applications that requires enhanced interaction of light and matter.