Collimation and finite-size effects in suspended resonant guided-mode gratings

TL;DR

This paper investigates how beam focusing and finite size influence the optical transmission in suspended resonant guided-mode gratings, combining experimental measurements with a coupled mode model for improved design insights.

Contribution

It introduces a phenomenological coupled mode model that accurately predicts finite-size and focusing effects in suspended gratings, aiding their optimization.

Findings

Model predictions agree well with experimental spectra

Finite-size and focusing effects significantly impact transmission

Results assist in designing better photonic and sensing devices

Abstract

The optical transmission of resonant guided-mode gratings patterned on suspended silicon nitride thin films and illuminated at normal incidence with a Gaussian beam are investigated both experimentally and theoretically. Effects due to the beam focusing and its finite size are accounted for by a phenomenological coupled mode model whose predictions are found to be in very good agreement with the experimentally measured spectra for various grating structures and beam sizes, and which allow for a detailed analysis of the respective magnitude of these effects. These results are highly relevant for the design and optimization of such suspended structured films which are widely used for photonics, sensing and optomechanics applications.