Dispersion extraction with near-field measurements in periodic waveguides

TL;DR

This paper introduces a high-resolution spectral method using near-field measurements and Bloch-wave symmetry to accurately extract mode dispersion in periodic waveguides, surpassing traditional Fourier-transform limitations.

Contribution

The authors develop and experimentally validate a spectral technique that accurately characterizes both propagating and evanescent modes in compact periodic waveguides using near-field data.

Findings

Achieved dispersion extraction with several percent accuracy.

Successfully characterized forward and backward wave amplitudes.

Demonstrated method's effectiveness on various waveguide configurations.

Abstract

We formulate and demonstrate experimentally the high-resolution spectral method based on Bloch-wave symmetry properties for extracting mode dispersion in periodic waveguides from measurements of near-field profiles. We characterize both the propagating and evanescent modes, and also determine the amplitudes of forward and backward waves in different waveguide configurations, with the estimated accuracy of several percent or less. Whereas the commonly employed spatial Fourier-transform (SFT) analysis provides the wavenumber resolution which is limited by the inverse length of the waveguide, we achieve precise dispersion extraction even for compact photonic structures.