Normal incidence narrowband transmission filtering in zero-contrast gratings

TL;DR

This paper introduces a narrowband optical filter using zero-contrast gratings that achieves high quality factors and broad wavelength applicability, with simple fabrication and tunability via guided modes.

Contribution

It demonstrates a novel zero-contrast grating design for narrowband filtering at normal incidence, with high Q-factors and broad spectral range applicability.

Findings

Quality factor exceeds 10^6.

Filter operates across near-infrared to terahertz.

Simple fabrication and integration into optical systems.

Abstract

We report narrowband transmission filtering based on zero-contrast grating (ZCG) reflectors at normal incidence. Computational results show that the filtering is realized through symmetry-protected modes coupling. The guided modes introduced by the slab layer make the filter frequencies flexible to modify. The rectangular structure of the filter allows simple fabrication and integration into optical systems. The quality factor of the filters could exceed 106. Owing to the low refraction index dispersion of the semiconductor and their scale-invariant operations, these filters can be applied in a broad infrared range from near infrared to terahertz wavelengths.