Brillouin scattering between optical and acoustic waves can be optimised by ensuring that they propagate through the same part – typically the core – of a waveguide. However, ensuring that co-localisation turns out to be rather tricky! For example, a standard rib waveguide with silicon core and silica substrate will happily guide optical waves in silicon (which supports light propagating slower than in silica), but the acoustic waves will leak out into the substrate. That’s because acoustic waves in silica propagate slower than in silicon.
We’ve written several papers on addressing this problem, either by smart engineering of the waveguides (here), or using different guidance mechanisms (here and here). Now, in a paper led by Lisa-Sophie Haerteis and Andy Boes from the University of Adelaide, and collaborators around the globe, we’ve demonstrated Brillouin scattering in suspended lithium niobate waveguides. This paper is published as APL Photonics 10, 096112 (2025).
Mikołaj K. Schmidt 