26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Multidimensional Brillouin–Kerr Frequency Combs in Surface Nanoscale Axial Photonic Resonators

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Speaker

Lewis Hill (Max Planck Institute for the Science of Light)

Description

Surface nanoscale axial photonic resonators (SNAPRs) provide a unique nonlinear photonics platform in which nanoscale effective-radius variations create axially confined whispering-gallery modes while preserving ultra-high optical quality factors. Theoretical studies have predicted that this axial confinement can fundamentally alter frequency-comb generation dynamics, while recent experiments have demonstrated Kerr-comb formation in SNAPRs [1,2].

Here, we investigate multidimensional frequency-comb generation arising from the interplay of Kerr four-wave mixing, stimulated Brillouin scattering (SBS), and axial mode confinement in silica SNAPRs. Building upon previous studies of two-dimensional comb formation in bottle resonators [3], we report frequency combs with line spacings corresponding directly to the axial mode structure of the resonator, enabling repetition rates approaching the GHz regime in sub-millimetre-scale devices. We additionally observe Brillouin-mediated comb multiplexing, where cascaded SBS generates multiple intracavity pump fields that independently seed Kerr-comb formation, producing coexisting comb families separated by the Brillouin frequency shift.

Low-power transmission spectrogram measurements are used to characterize the passive modal structure of the resonators, revealing the effective-radius profile, axial confinement, and mode families supporting the observed nonlinear dynamics. The resulting spectra exhibit multiple characteristic frequency scales associated with azimuthal, axial, and Brillouin-mediated processes, highlighting the inherently multidimensional nature of comb formation in axially structured resonators.

We present initial theoretical efforts aimed at understanding the coupling between these nonlinear processes and the mechanisms governing multidimensional comb formation. These results establish SNAPRs as a promising platform for studying nonlinear wave dynamics across multiple spectral and spatial scales, with potential applications in microwave photonics, spectroscopy, optical communications, and precision metrology.

References:
[1] Suchkov et al., Opt. Lett. 42, 2149–2152 (2017);
[2] Eadie et al., Opt. Express 33, 34677–34687 (2025);
[3] Jin et al., Photonics Res. 9, 171–180 (2021).