Brillouin spectroscopy of a hybrid silicon-chalcogenide waveguide with geometrical variations

TL;DR

This paper investigates how deliberate geometrical variations in hybrid silicon-chalcogenide waveguides affect their localized Brillouin response, using distributed Brillouin measurements to assess uniformity and interaction strength.

Contribution

It introduces a method to design and fabricate waveguides with controlled width variations and demonstrates their impact on Brillouin scattering properties.

Findings

Geometrical variations significantly influence Brillouin resonance locations.

Distributed Brillouin measurements effectively map localized opto-acoustic responses.

Design insights can optimize waveguide uniformity and SBS interaction.

Abstract

Recent advances in design and fabrication of photonic-phononic waveguides have enabled stimulated Brillouin scattering (SBS) in silicon-based platforms, such as under-etched silicon waveguides and hybrid waveguides. Due to the sophisticated design and more importantly high sensitivity of the Brillouin resonances to geometrical variations in micro- and nano-scale structures, it is necessary to have access to the localized opto-acoustic response along those waveguides to monitor their uniformity and maximize their interaction strength. In this work, we design and fabricate photonic-phononic waveguides with a deliberate width variation on a hybrid silicon-chalcogenide photonic chip and confirm the effect of the geometrical variation on the localized Brillouin response using a distributed Brillouin measurement.