Surface plasmon-polariton resonance at diffraction of THz radiation on semiconductor gratings

TL;DR

This study investigates the resonance diffraction of THz radiation on semiconductor gratings, demonstrating how surface plasmon-polariton resonances can be observed and manipulated through surface modifications, with theoretical models aligning with experimental results.

Contribution

It presents a simple analytical theory for resonance diffraction on semiconductor gratings with dielectric layers, matching experimental observations and aiding sensing applications.

Findings

Resonance diffraction causes suppression of specular reflectivity.

Presence of a dielectric layer shifts and broadens the resonance.

Analytical expressions accurately describe resonance shifts and broadening.

Abstract

Resonance diffraction of THz HCN laser radiation on a semiconductor (InSb) grating is studied both experimentally and theoretically. The specular reflectivity suppression due to the resonance excitation of the THz surface plasmon-polariton is observed on a pure semiconductor grating and on semiconductor gratings covered with a thin striped layer of the residual photoresist. Presence of a thin dielectric layer on the grating surface leads to the shift and widening of the plasmon-polariton resonance. A simple analytical theory of the resonance diffraction on a shallow grating covered with a dielectric layer is presented. Its results are in a good accordance with the experimental data. Analytical expressions for the resonance shift and broadening can be useful for sensing data interpretation.