Two-groove narrowband transmission filter integrated in a slab waveguide

TL;DR

This paper introduces a simple integrated narrowband filter with two grooves on a slab waveguide that achieves high selectivity and tunability for potential use in waveguide spectrometers.

Contribution

It presents a novel design of a narrowband filter using two grooves on a slab waveguide, enabling controlled spectral filtering at oblique incidence.

Findings

Achieves zero reflectance and unity transmittance at resonance

Transmittance peak width and position are tunable by groove and ridge dimensions

Potential application in integrated waveguide spectrometers

Abstract

We propose a simple integrated narrowband filter consisting of two grooves on the surface of a slab waveguide. Spectral filtering is performed in transmission at oblique incidence due to excitation of an eigenmode of the structure localized at a ridge cavity between the grooves. For the considered parameters, strictly zero reflectance and unity transmittance are achieved at resonant conditions. Width and location of the transmittance peak can be controlled by changing the widths of the grooves and of the ridge, respectively. The proposed filter may find application in waveguide-integrated spectrometers.