Waveguiding power of photonic crystal slabs

TL;DR

This paper introduces the concept of guiding power to describe waveguiding in photonic crystal slabs, demonstrating enhanced TM wave confinement through local field effects, with implications for infrared and THz laser design.

Contribution

It develops a theoretical framework for waveguiding in photonic crystal slabs using the guiding power parameter, accounting for local field corrections and polarization differences.

Findings

Guiding power effectively describes wave spectra in thin slabs.

Enhanced TM wave confinement in porous and structured layers.

Potential applications in designing infrared and THz lasers.

Abstract

We consider the waveguiding by thin patterned slabs embedded in a homogeneous medium. In the longwave limit, the wave spectra of slabs are found to be well described by a single frequency-independent parameter, which we call the "guiding power". The guiding power can be evaluated in an effective medium approximation, similar to the Maxwell Garnett theory, but modified for the local field corrections specific to the two-dimensional geometry. The guiding power is different for the transverse magnetic (TM) and transverse electric (TE) polarizations. We show that the confinement factor of TM waves in a porous layer with high index ratio can exceed that for a homogeneous layer. Similarly enhanced confinement of TM waves is demonstrated for a layer of elongated cylinders or elliptic inclusion with a high axis length ratio. The effect originates from the suppression of local field effects and the increasing internal field in the inclusion. It may be useful in the design of far-infrared or THz quantum cascade lasers.