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

Normal- and Anomalous-Dispersion Frequency Combs in Pulse-Driven Passive Kerr Resonators Enabled by Raman Scattering

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Speaker

Jordan Wise (University of Auckland)

Description

Optical frequency combs (OFCs) are broadband coherent light sources composed of tens to thousands of equally spaced narrow spectral lines that have revolutionised many optical metrology tasks. OFCs have been demonstrated using a soliton circulating in an externally driven passive Kerr resonator. Standard cavity solitons are produced in optical cavities with anomalous dispersion and are spectrally pinned to the wavelength of their pump field. Recent work leveraging stimulated Raman scattering, group velocity dispersion (GVD) and desynchronised pulsed driving has produced ultrashort solitons whose centre wavelength is displaced significantly from that of the pump [1]. However, to produce these solitons, desynchronisation must be set so that the soliton is phase-matched with the pump, tightly restricting both the usable range of desynchronisation values and the achievable range of soliton centre wavelengths.

In this work, we first find a family of wavelength-displaced solitons which do not require phase matching, enabling a wider range of desynchronisation values to be used, allowing us to control the repetition rate of our solitons, and therefore the line spacing of the corresponding frequency comb. Because of GVD, changing the repetition rate also changes the soliton centre wavelength. Further, we find that by suppressing the solitons which form in the anomalous dispersion region with careful loss engineering of our cavity, we are also able to produce stable optical structures in the normal dispersion regime. The optical spectrum of these normal-dispersion combs is much flatter than the equivalent soliton combs, which may be desirable for tasks like precision spectroscopy. As with our non-phase-locked solitons, these normal dispersion structures do not require phase matching, and so their repetition rate and centre wavelength can readily be tuned.

Reference
[1] Z. Li et al., “Ultrashort dissipative Raman solitons in Kerr resonators driven with phase-coherent optical pulses,” Nature Photonics, vol. 18, pp. 46–53, 2022.